RUSTSEC-2026-0097: Rand is unsound with a custom logger using `rand::rng()`
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- Rust
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Description
| Details | |
|---|---|
| Package | rand |
| Version | 0.9.2 |
| Warning | unsound |
| URL | https://github.com/rust-random/rand/pull/1763 |
| Patched Versions | >=0.10.1 OR <0.10.0, >=0.9.3 OR <0.9.0, >=0.8.6 |
| Unaffected Versions | <0.7.0 |
| Aliases | GHSA-cq8v-f236-94qc |
It has been reported (by @lopopolo) that the rand library is unsound (i.e. that safe code using the public API can cause Undefined Behaviour) when all the following conditions are met:
- The
logandthread_rngfeatures are enabled - A custom logger is defined
- The custom logger accesses
rand::rng()(previouslyrand::thread_rng()) and calls anyTryRng(previouslyRngCore) methods onThreadRng - The
ThreadRng(attempts to) reseed while called from the custom logger (this happens every 64 kB of generated data) - Trace-level logging is enabled or warn-level logging is enabled and the random source (the
getrandomcrate) is unable to provide a new seed
TryRng (previously RngCore) methods for ThreadRng use unsafe code to cast *mut BlockRng<ReseedingCore> to &mut BlockRng<ReseedingCore>. When all the above conditions are met this results in an aliased mutable reference, violating the Stacked Borrows rules. Miri is able to detect this violation in sample code. Since construction of aliased mutable references is Undefined Behaviour, the behaviour of optimized builds is hard to predict.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by locating the SDK dependency manifests and checking why rand 0.9.2 is selected. Compare the resolved version with the patched versions listed in the advisory, then run the repository's Rust checks to confirm the vulnerable version is no longer used.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- security
- Issue type
- Bug
- Difficulty
- 2/5
- Estimated time
- 1-3 hours
- Activity status
- Quiet
- Clarity
- Needs clarification
- Newbie friendliness
- 38/100