GoFetch Vulnerability Revealed


A Silent Threat to Cryptographic Security

Breaking Constant-Time Cryptographic Implementations Using Data Memory-Dependent Prefetchers

Read on to see the GoFetch Vulnerability revealed.

In what is now a disturbing trend – see my posts here and here  – US University researchers have uncovered yet another unpatchable critical security flaw in Apple’s M-series chips, or Apple Silicon – the vaunted M1, M2 & M3 CPUs. Dubbed “GoFetch,” detailed on the delightfully named gofetch.fail website, this vulnerability poses a significant risk to cryptographic security and has far-reaching implications for users.

GoFetch Vulnerability Explained

GoFetch is a side-channel attack that targets Apple’s M1, M2, and M3 processors. Unlike traditional software vulnerabilities, GoFetch exploits a microarchitectural design flaw inherent in the silicon itself. This means that patching it directly is impossible. Instead, mitigation efforts must focus on third-party cryptographic software, which unfortunately comes at a cost: performance degradation.

How GoFetch Works

At the heart of the issue lies the data memory-dependent prefetcher (DMP) within Apple’s chips. The DMP predicts memory addresses that running code is likely to access, preloading data into the CPU cache to reduce latency. However, this optimization inadvertently creates a side channel that attackers can exploit.

When a targeted cryptographic operation and a malicious application with normal user system privileges run on the same CPU cluster, GoFetch comes into play. The DMP occasionally confuses memory content (such as cryptographic keys) with pointer values used for data access. As a result, it reads the data and attempts to treat it as an address, leaking sensitive information. 

But how do we use it?  The researchers have promised a public release is coming soon – get it from the github repo.

The Constant-Time Paradigm

Cryptographic engineers have long used constant-time programming to prevent side-channel attacks. This approach ensures that all operations take the same amount of time, regardless of secret-dependent memory accesses. Unfortunately, GoFetch violates this paradigm by dereferencing pointers and leaking data through a side channel.

Impact and Mitigation

Mitigating GoFetch involves a delicate balance. Building defenses into cryptographic software can limit the vulnerability’s impact, but it comes at the cost of performance. Especially on earlier M1 and M2 generations, executing cryptographic operations may suffer significant slowdowns.

Protecting Your Mac

As a Mac user, what can you do to safeguard your data? Here are some steps:

  1. Stay Informed: Keep an eye on security updates and advisories from Apple. While GoFetch cannot be directly patched, Apple may release guidance on mitigating its impact.
  2. Choose Third-Party Software Wisely: If you rely on cryptographic applications, ensure they follow best practices for constant-time programming. Some software may implement workarounds to minimize GoFetch’s effects.
  3. Limit Exposure: Be cautious about running untrusted applications alongside sensitive cryptographic operations. Isolate critical tasks whenever possible.
Gofetch Vulnerability Revealed


GoFetch serves as a stark reminder that even cutting-edge hardware can harbor vulnerabilities. As the security community grapples with this new threat, users must remain vigilant. While we await further guidance from Apple, understanding the risks and taking informed precautions can help protect our digital lives.

Remember, the invisible enemy can be the most dangerous. GoFetch may not be visible, but its impact is real, and we must adapt accordingly.