GHSA-x4gp-pqpj-f43q
LOWGHSA-x4gp-pqpj-f43q is a low-severity (CVSS 2.9) CWE-733 vulnerability in curve25519-dalek. O3 Security confirms whether GHSA-x4gp-pqpj-f43q is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
curve25519-dalek has timing variability in `curve25519-dalek`'s `Scalar29::sub`/`Scalar52::sub`
Blast Radius
curve25519-dalekReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
Timing variability of any kind is problematic when working with potentially secret values such as elliptic curve scalars, and such issues can potentially leak private keys and other secrets. Such a problem was recently discovered in curve25519-dalek.
The Scalar29::sub (32-bit) and Scalar52::sub (64-bit) functions contained usage of a mask value inside a loop where LLVM saw an opportunity to insert a branch instruction (jns on x86) to conditionally bypass this code section when the mask value is set to zero as can be seen in godbolt:
- 32-bit (see L106): https://godbolt.org/z/zvaWxzvqv
- 64-bit (see L48): https://godbolt.org/z/PczYj7Pda
A similar problem was recently discovered in the Kyber reference implementation:
https://groups.google.com/a/list.nist.gov/g/pqc-forum/c/hqbtIGFKIpU/m/cnE3pbueBgAJ
As discussed on that thread, one portable solution, which is also used in this PR, is to introduce a volatile read as an optimization barrier, which prevents the compiler from optimizing it away.
The fix can be validated in godbolt here:
- 32-bit: https://godbolt.org/z/jc9j7eb8E
- 64-bit: https://godbolt.org/z/x8d46Yfah
The problem was discovered and the solution independently verified by Alexander Wagner [email protected] and Lea Themint [email protected] using their DATA tool:
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | curve25519-dalek | all versions | 4.1.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for curve25519-dalek. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update curve25519-dalek to 4.1.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-x4gp-pqpj-f43q is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-x4gp-pqpj-f43q is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-x4gp-pqpj-f43q. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-x4gp-pqpj-f43q in your dependencies?
O3 detects GHSA-x4gp-pqpj-f43q across crates.io dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.