Rowhammer in the Wild: Large-Scale Insights from FlippyR.AM @ One
2025-12-29 23:00 - 23:40 (Europe/Berlin) | One @ 39C3 (de-en)
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Assignees: YETI, lucas

Speakers: Martin Heckel, Florian Adamsky, Daniel Gruss

Last year at 38c3, we gave a talk titled "Ten Years of Rowhammer: A Retrospect (and Path to the Future)."
In this talk, we summarized 10 years of Rowhammer research and highlighted gaps in our understanding.
For instance, although nearly all DRAM generations from DDR3 to DDR5 are vulnerable to the Rowhammer effect, we still do not know its real-world prevalence.
For that reason, we invited everyone at 38c3 last year to participate in our large-scale Rowhammer prevalence study.
In this year's talk, we will first provide an update on Rowhammer research and present our results from that study.

A lot has happened in Rowhammer research in 2025.
We have evidence that DDR5 is as vulnerable to Rowhammer as previous generations.
Other research shows that not only can adversaries target rows, but columns can also be addressed and used for bit flips.
Browser-based Rowhammer attacks are back on the table with Posthammer and with ECC. fail, we can mount Rowhammer attacks on DDR4 with ECC memory.

In our large-scale study, we measure Rowhammer prevalence in a fully automated cross-platform framework, FlippyR.AM, using the available state-of-the-art software-based DRAM and Rowhammer tools.
Our framework automatically gathers information about the DRAM and uses 5 tools to reverse-engineer the DRAM addressing functions, and based on the reverse-engineered functions, uses 7 tools to mount Rowhammer.
We distributed the framework online and via USB thumb drives to thousands of participants from December 30, 2024, to June 30, 2025. Overall, we collected 1006 datasets from 822 systems with various CPUs, DRAM generations, and vendors.
Our study reveals that out of 1006 datasets, 453 (371 of the 822 unique systems) succeeded in the first stage of reverse-engineering the DRAM addressing functions, indicating that successfully and reliably recovering DRAM addressing functions remains a significant open problem.
In the second stage, 126 (12.5 % of all datasets) exhibited bit flips in our fully automated Rowhammer attacks.
Our results show that fully automated, i.e., weaponizable, Rowhammer attacks work on a lower share of systems than FPGA-based and lab experiments indicated, but at 12.5%, are still a practical vector for threat actors.
Furthermore, our results highlight that the two most pressing research challenges around Rowhammer exploitability are more reliable reverse-engineering tools for DRAM addressing functions, as 50 % of datasets without bit flips failed in the DRAM reverse-engineering stage, and reliable Rowhammer attacks across diverse processor microarchitectures, as only 12.5 % of datasets contained bit flips.
Addressing each of these challenges could double the number of systems susceptible to Rowhammer and make Rowhammer a more pressing threat in real-world scenarios.
This will be a followup talk after our talk "Ten Years of Rowhammer: A Retrospect (and Path to the Future)" at 38C3.
In the talk last year we gave an overview of the current state of Rowhammer and highlighted that there are no large-scale prevalence studies.
We wanted to change that and asked the audience to participate in our large-scale study on Rowhammer prevalence.

We performed the large-scale study on Rowhammer prevalence thanks to many volunteers supporting our study by measuring their systems.
In total, we collected 1006 datasets on 822 different systems (some systems were measured multiple times).
We show that 126 of them (12.5%) are affected by Rowhammer with our fully-automated setup.
This should be seen as a lower bound, since the preconditions required for effective tools failed on ~50% of the systems.
Among many other insights, we learned that the fully-automated reverse-engineering of DRAM addressing functions is still an open problem and we assume the actual number of affected systems to be higher as the 12.5% we measured in our study.

Now, one year after our talk at the 38C3, we want to give an update on the current state of Rowhammer, since multiple new insights were published in the last year:
The first reliable Rowhammer exploit on DDR5, a JavaScript implementation of Rowhammer that works on current DDR4 systems, and an ECC bypass on DDR4, just to name a few.
Additionally, we want to present the results of our large-scale study on Rowhammer prevalence which was supported by the audience from last year's talk.

Battling Obsolescence – Keeping an 80s laser tag system alive @ Fuse
2025-12-30 13:50 - 14:30 | Fuse @ 39C3 (de-en)
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Assignees: YETI, os10000

Speakers: Trikkitt

Keeping old projects working can be an uphill battle. This talk explores how the laser tag system Q-Zar (Quasar in the UK) has been kept alive since the company behind it failed in the 90s. The challenges encountered, the lessons learnt, and how those can be applied to our own future projects to maximise the project lifetime.
Looking at the effects of obsolescence in the context of a laser tag system from the 1980s Q-Zar (Quasar in the UK), what needed to happen to keep it going to enable people to continue playing. What lessons we can learn from that and some good examples from other projects, and how that can be applied to our own projects.

This talk covers the electronics involved in the laser tag system, why the continued availability of components has varied a lot. The need to develop new computer software that continues to work years later. The way the physical equipment can have its life extended.

Topics covered range from electronics design through to software coding and onto physical unit repair. A look at the tooling created to help maintain, support and repair the laser tag packs. The challenges Covid-19 created and how things were rapidly pivoted to enable continued playing in challenging times.
This is about how we all can make simple decisions that help build something that will last the maximum time possible with the least amount of effort.

[CANDIDATE] Race conditions, transactions and free parking @ Zero
2025-12-29 21:05 - 21:45 | Zero @ 39C3 (de-en)
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Current Assignees: cv, 42triangles

Other Candidates: phmy, cv, flo_h, Stormwind, 42triangles, oskar, pinkdispatcher, Beni, kaste

Speakers: Benjamin W. Broersma

ORM's and/or developers don't understand databases, transactions, or concurrency.
After the Air France-KLM dataleak I kept repeating this was not a real hack, and confessed I always wanted to hack a system based on triggering race conditions because the lack of proper transactions.
This was way easier than expected. In this talk I will show how just adding $ seq 0 9 | xargs -I@ -P10 .. can break some systems, and how to write safe database transactions that prevent abuse.

In this talk I will explain what race conditions are. Many examples of how and why code will fail. How to properly create a database transaction. The result of abusing this in real life (e.g. free parking).

[CANDIDATE] Spectre in the real world: Leaking your private data from the cloud with CPU vulnerabilities @ Zero
2025-12-30 00:15 - 00:55 | Zero @ 39C3 (de-en)
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Current Assignees: phmy, pinkdispatcher

Other Candidates: ItsKiwi, phmy, cv, pinkdispatcher

Speakers: Thijs Raymakers

Transient execution CPU vulnerabilities, like Spectre, have been making headlines since 2018. However, their most common critique is that these types of vulnerabilities are not really practical. Even though it is cool to leak /etc/shadow with a CPU bug, it has limited real-world impact. In this talk, we take Spectre out for a walk and let it see the clouds, by leaking memory across virtual machine boundaries at a public cloud provider, bypassing mitigations against these types of attacks. Our report was awarded with a $151,515 bug bounty, Google Cloud's highest bounty yet.
Seven years ago, Spectre and Meltdown were announced. These two vulnerabilities showed that instructions executed by the CPU might accidentally access secret data. This secret data can contain files cached from disk, cryptographic keys, private information, or anything else that might be stored in memory. An attacker can use Spectre to learn the value of that secret data, even though the attacker is not supposed to have access to it.

Even though this sounds problematic, there is a reason why these type of vulnerabilities haven't had a significant real-world impact. Mitigations make it much harder to pull off, and an attacker needs a form of remote code execution anyway to trigger the relevant CPU instructions. If an attacker can already execute arbitrary code, then Spectre is probably not what you should be worried about. For regular users, these CPU vulnerabilities are likely not that much of a threat.

However, that is not the case for public cloud providers. Their business model is to provide remote code execution as a service, and to rent out shared hardware resources as efficiently as possible. Customers run their system in an seemingly isolated virtual machine on top of shared physical hardware. Because customers can run anything they want on these systems, public cloud providers must treat these workloads as untrusted. They have to assume the worst case scenario, i.e. that an attacker is deliberately trying violate the confidentiality, integrity or availability of their systems, and, by extension, their customers' systems. For transient execution vulnerabilities like Spectre, that means that they enable all reasonable mitigations, and some more.

In this talk, we show that transient execution attacks can be used on real-world systems, despite the deployed software mitigations. We demonstrate this by silently leaking secret data from another virtual machine at a major global cloud provider, defeating virtual machine isolation without leaving a trace. Additionally, we'll discuss our coordinated disclosure process, the currently deployed mitigations and how future mitigations could address the issue.

[CANDIDATE] Light in the Dark(net) @ Zero
2025-12-29 22:05 - 22:45 | Zero @ 39C3 (de-en)
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Current Assignees: ruffleduffle, haris

Other Candidates: yote, phmy, caluera, haris, kwii, derdre, Beni, ruffleduffle

Speakers: Tobias Höller

Science is hard and research into the usage of the Tor network is especially so. Since it was designed to counter suveillance, it gathering reliable information is difficult. As a consequence, the studies we do have, have yielded very different results.

This talk investigates the root causes of contradicting studies by highlighting how slight changes in methodology or data selection completely change the results and thereby our understanding of what the Darknet is. Whether you consider it the last bastion of freedom or a haven of crime, this talk will tell you where to look and what to ignore in order to confirm your current opinion. And in case you are open to changing it, we have some food for thought for you.
Onion services can be considered one of the most controversial aspects of the Tor network, because they allow the anonymous hosting of services, which has enabled the creation of illegal services which are difficult for law enforcement to shut down. Defenders argue that this is a price worth paying to ensure free speech for people who could otherwise not speak up or run their own services.

This obviously raises the question what onion services are being actually used for in practice. Many researchers have tried to answer this question in the past. Based on their work we already know a few things:

9% of all Websites on the Darknet are marketplaces [1]
2.7% of all Websites on the Darknet are marketplaces [2]
50% of all Websites on the Darknet are marketplaces [3]
8.4% of all Websites on the Darknet are marketplaces [4]
27% of all Websites on the Darknet are marketplaces [5]
34.8% of all Websites on the Darknet are marketplaces [6]

No, this is not a copy and paste error, all of the above statements can be found in peer-reviewed scientific publications. All of these results are valid on their own and constitute valuable contributions to science, but it does not take an expert to notice the contradictions in their findings.
The reasons for these inconsistencies are the main topic of this talk. We will discuss the information available to researchers and the limitations originating from it. Challenges and current disagreements when it comes to interpreting available data will be addressed along with common misrepresentations of research results. We will highlight how the choice of data sources can predetermine the final result before a study has even begun, how minor changes to definitions can lead to completely different results and how important context is when interpreting data.

Armed with this knowledge, we can tackle the challenge to find out what we know about the Darknet, what we might figure out in the future, what we can reasonably assume but will never be able to prove, and what we will (hopefully) never know.

Sources
[1] https://doi.org/10.1049/iet-ifs.2015.0121
[2] https://doi.org/10.1016/j.future.2024.03.025
[3] https://doi.org/10.1145/3600160.3600167
[4] https://doi.org/10.1109/INFOCOM53939.2023.10229057
[5] https://doi.org/10.1109/ICDCSW.2014.20
[6] https://doi.org/10.1080/00396338.2016.1142085

[CANDIDATE] Atoms in Space @ Ground
2025-12-30 11:00 - 11:40 | Ground @ 39C3 (de-en)
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Current Assignees: alphabetcurl

Other Candidates: phmy, eskarina, kythra, alphabetcurl

Speakers: manuel

What are atoms doing in space anyways? This talk will provide a brief overview of applications of quantum technologies in space ranging from precise timing and inertial measurements to fundamental physics.
Quantum technologies have seen a wide field of applications in medicine, geosciences, computing and communications, in many cases bridging the gap from laboratory experiments to commercial products in the last decade. For terrestrial applications that is. But what about going to space?

Quantum physics based sensors and experiments promise higher accuracy, sensitivity or better long term stability as they rely on immutable properties of atoms. When properly manipulated, these (ultra-)cold atoms are likely to outperform state of the art instruments. Experiments conducted on sounding rockets demonstrated important steps like Bose-Einstein Condensate creation during a few minutes in microgravity, enabling more advanced quantum experiments in the future. The International Space Station and the Tiangong Space Station host dedicated experiments like ultrastable clocks as well as flexible research infrastructure for fundamental research benefitting from long free-fall times. However, the deployment of such technologies on satellites is not as advanced. Satellite missions utilizing quantum sensors or performing long term experiments are subject to studies and proposals backed by a broad scientific community aiming at better understanding of climate change, interplanetary navigation or tests of general relativity. First steps towards realization of such missions are taken by ESA, NASA and various national space agencies as well as universities funded by national agencies or the EU.

This talk will detect the current state of atoms in space and give an overview of active programs to deploy quantum sensors on operational satellite missions. The focus is on future applications in geosciences and related fields employing the same technology.

[CANDIDATE] How to keep Open Source open without leaving our communities open to threats @ Fuse
2025-12-30 11:00 - 11:40 | Fuse @ 39C3 (de-en)
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Current Assignees: katzenzunge, Beni

Other Candidates: B., hoedur, katzenzunge, Beni, os10000, scherrie

Speakers: Quintessence

The Four Freedoms (defined ~40 years ago) and the Four Opens (~15 years ago) for Open Source provided canonical definitions for what are the cornerstones of Open Source Software communities today. While the ethos still applies today, the cultural norms that blossomed to put it into practice are from an era with different challenges.

To build a better world, we need to both keep and protect the value system of the Four Freedoms and Four Opens. To do that, we need to re-assess our risk and threat models to balance that allows beautiful minds to flourish as well as introduce responsible friction to prevent harm from coming to them.
The state of the internet, c 1990:

Limited, opt-in connectivity: people had to both have access to a computer and that computer had to have access to the internet.
Tooling required some in-industry knowledge to be able to run and use, not only for development but also for communication.
Open source was a young movement. The "common source" was proprietary.

The state of the internet, c 2025:

Always online, might-not-even-be-to-opt-out connectivity: devices are almost always collecting and transmitting data, including audio/visual, in some cases even if "turned off".
Easy to use tooling has made it easier for everyone to come together. The pervasiveness of technology also means that most people, of any background, can easily access other people in the thousands or even millions.
Open source is common, accessible, and matured. A $9 trillion resource. Yes, trillion.

These three significant changes drastically change the threat model for OSS communities. In the beginning, someone had to have both knowledge and resources to harm or otherwise compromise a community of developers. Now, anyone with a grudge can make a bot army with seamless integrations and gracious freemium tiers for AI/LLMs. Likewise, when open source was small, the "who" who would be motivated to harm and otherwise disrupt those communities was limited. Now there is both massive social and economic benefit to harm and disrupt. This means that risks and threats now still include the motivated and resourced with the addition of those who are scarce in both.

We need to come together to build new organizational threat models that account for how this consequence has posed new risks to our communities. With care and attention to detail, we can introduce responsible friction that will protect our communication infrastructure, the lifeblood of what allows open source to grow.

There will also be a workshop with this presentation, with the outcome of creating an ongoing working group dedicated to helping OSS Foundations of all sizes protect their communities.

There will be a workshop about the same topic on 12.30, Day 4: https://events.ccc.de/congress/2025/hub/de/event/detail/how-to-keep-open-source-open-without-leaving-our-c

[CANDIDATE] Von Fuzzern zu Agenten: Entwicklung eines Cyber Reasoning Systems für die AIxCC @ Fuse
2025-12-29 23:00 - 2025-12-30 00:00 | Fuse @ 39C3 (de-en)
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Current Assignees: Lilotimeline, Beni

Other Candidates: tribut, phmy, Beni, Lilotimeline, os10000, kwii

Speakers: Mischa Meier (mmisc), Annika Kuntze

Die AI Cyber Challenge (AIxCC) der DARPA hatte zum Ziel, die Grenzen der autonomen Cybersicherheit zu erweitern: Können AI-Systeme Software-Schwachstellen unabhängig, in Echtzeit und ohne menschliche Hilfe identifizieren, verifizieren und beheben?
Im Laufe von zwei Jahren entwickelten Teams aus aller Welt „Cyber Reasoning Systems“ (CRS), die in der Lage sind, komplexe Open-Source-Software zu analysieren, Code zu analysieren, reproducer zu generieren, um zu zeigen, dass ein gemeldeter Fehler kein Fehlalarm ist, und schließlich Patches zu synthetisieren.
Unser Team nahm an dieser Challenge teil und entwickelte von Grund auf ein eigenes CRS. In diesem Vortrag geben wir Einblicke in den Wettbewerb: Wie funktioniert die LLM-gesteuerte Schwachstellenerkennung tatsächlich, welche Designentscheidungen sind wichtig und wie sind die Finalisten-Teams an das Problem herangegangen?
Die AIxCC (DARPA’s AI Cyber Challenge) ist ein zweijähriger Wettbewerb, dessen Ziel es war, die Möglichkeiten der automatisierten Erkennung und Behebung von Sicherheitslücken zu verbessern.
Dabei sollte ein autonomes, in sich geschlossenes System entwickelt werden, das Software analysiert, Schwachstellen erkennt, diese mithilfe von Reproducern nachweist und anschließend sichere Patches erzeugt.

Unser Team hat sich diesem globalen Experiment angeschlossen und ein eigenes Cyber Reasoning System (CRS) von Grund auf neu entwickelt. Dazu haben wir mehrere Agenten entwickelt. Unser System profitierte von der Kombination klassischer Techniken wie Fuzzing mit modernen Large Language Models (LLMs). Die Synergie zwischen diesen Ansätzen erwies sich als leistungsfähiger als jede der beiden Techniken für sich allein, sodass unser CRS Software auf eine Weise untersuchen und patchen konnte, wie es weder Fuzzing noch LLMs allein leisten konnten.

In diesem Vortrag werden wir:
- das Konzept und die Ziele hinter AIxCC erläutern
- durchgehen, wie ein CRS tatsächlich funktioniert und wie wir unseres entwickelt haben
- zeigen, wie LLMs traditionelle Fuzzing- und Analyse-Techniken unterstützen können
- Beobachtungen zu den Strategien der Finalisten-Teams teilen

[CANDIDATE] CCC&T - Cosmic ray, the Climate Catastrophe and Trains. @ One
2025-12-30 11:55 - 12:35 | One @ 39C3 (de-en)
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Current Assignees: yote, Lilotimeline

Other Candidates: pinkdispatcher, phmy, Lilotimeline, nebelwirkung, yote

Speakers: FantasticMisterFux, louiT

How can we predict soil moisture by measuring cosmic ray products and what have trains to do with it? Ever wondered how this Dürremonitor works, that you heared about in ther german news? These question and some more I will try to answer while I give an overview of some of the research that is done by the Helmholtz Centre for Environmental Research (UFZ).
The Dürremonitor is a programme that is often mentioned in the German news when some regions experience drought. Alongside the Dürremonitor and the underlying Mesoscale Hydrological Model (MHM), there is ongoing research at the UFZ concerning soil moisture. Some of these studies involve measuring soil moisture using a technique called cosmic ray neutron sensing (CRNS). Rather than taking measurements, the MHM uses a physics-based model incorporating precipitation forecasts to predict drought or flood. These two strategies for quantifying soil moisture are therefore in opposition: the measurement-based approach (CRNS) and the modelling-based approach (MHM/Dürremonitor). CRNS is a relatively new method of measuring soil moisture based on the proportion of neutrons reflected by the soil (the principles were discovered in the 1980s, but it has only recently become commercially applicable). This method has several advantages over previous soil moisture measurement methods: it is non-invasive, easy to set up, portable and can therefore be used on trains.

In the talk I will give an overview of the Dürremonitor and MHM and then focus on CRNS. I will explain the physical principles behind the method, how it is implemented in practice by making serveys using trains.
