GHSA-857q-xmph-p2v5 is a medium-severity (CVSS 4.8) vulnerability in s2n-tls. A fix is available for s2n-tls — see the affected versions and patch details below.
s2n-tls's mTLS API ordering may skip client authentication
Real-World Exposure
s2n-tlsReal-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
Impact
An API ordering issue in s2n-tls can cause client authentication to unexpectedly not be enabled on the server when it otherwise appears to be. Server applications are impacted if client authentication is enabled by calling s2n_connection_set_config() before calling s2n_connection_set_client_auth_type().
Applications are not impacted if these APIs are called in the opposite order, or if client authentication is enabled on the config with s2n_config_set_client_auth_type(). s2n-tls clients verifying server certificates are not impacted.
Impacted versions: < v1.5.0.
Patches
The patch is included in v1.5.0 [1].
Workarounds
Applications can workaround this issue by calling s2n_connection_set_config() after calling s2n_connection_set_client_auth_type(), or by enabling client authentication on the config with s2n_config_set_client_auth_type().
If you have any questions or comments about this advisory we ask that you contact AWS/Amazon Security via our vulnerability reporting page [2] or directly via email to [email protected]. Please do not create a public GitHub issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | s2n-tls | all versions | 0.3.0cargo update -p s2n-tls --precise 0.3.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for s2n-tls, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update s2n-tls to 0.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-857q-xmph-p2v5 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-857q-xmph-p2v5 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-857q-xmph-p2v5. 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-857q-xmph-p2v5 in your dependencies?
O3 Security finds GHSA-857q-xmph-p2v5 across crates.io dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.