GHSA-x4mj-7f9g-29h4
HIGHGHSA-x4mj-7f9g-29h4 is a high-severity (CVSS 8.1) remote code execution vulnerability in github.com/projectcontour/contour. O3 Security confirms whether GHSA-x4mj-7f9g-29h4 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Contour has Lua code injection via Cookie Path Rewrite Policy
Blast Radius
github.com/projectcontour/contour🐹github.com/projectcontour/contour🐹github.com/projectcontour/contourReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Impact
Contour's Cookie Rewriting feature is vulnerable to Lua code injection. An attacker with RBAC permissions to create or modify HTTPProxy resources can craft a malicious value in the following fields that results in arbitrary code execution in the Envoy proxy:
spec.routes[].cookieRewritePolicies[].pathRewrite.valuespec.routes[].services[].cookieRewritePolicies[].pathRewrite.value
The cookie rewriting feature is internally implemented using Envoy's HTTP Lua filter. User-controlled values are interpolated into Lua source code using Go text/template without sufficient sanitization.
The injected code only executes when processing traffic on the attacker's own route, which they already control. However, since Envoy runs as shared infrastructure, the injected code can also:
- Read Envoy's xDS client credentials from the filesystem, which could be used to read all Contour xDS configuration, including TLS certificates and private keys of other tenants.
- Cause denial of service for other tenants sharing the Envoy instance.
Other use cases of Lua filter are not vulnerable.
Patches
The fix is available in Contour v1.33.4, v1.32.5, and v1.31.6.
- v1.33.4: User-provided values are no longer interpolated into Lua code. Use of
text/templateis removed. Requires Envoy 1.35.0 or later. - v1.32.5, v1.31.6: User-provided values are escaped before interpolation into Lua code.
Workarounds
There are no workarounds. Users should upgrade to a patched version.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/projectcontour/contour | ≥ 1.19.0&&< 1.31.6 | 1.31.6 |
| 🐹Go | github.com/projectcontour/contour | ≥ 1.32.0&&< 1.32.5 | 1.32.5 |
| 🐹Go | github.com/projectcontour/contour | ≥ 1.33.0&&< 1.33.4 | 1.33.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/projectcontour/contour. 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 github.com/projectcontour/contour to 1.31.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-x4mj-7f9g-29h4 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-x4mj-7f9g-29h4 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-x4mj-7f9g-29h4. 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-x4mj-7f9g-29h4 in your dependencies?
O3 detects GHSA-x4mj-7f9g-29h4 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.