GHSA-857q-xmph-p2v5
MEDIUMs2n-tls's mTLS API ordering may skip client authentication
Blast Radius
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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 | 0.3.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for s2n-tls. 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 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 pinpoints whether GHSA-857q-xmph-p2v5 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-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 detects GHSA-857q-xmph-p2v5 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.