Envoy Gateway: Authentication Bypass via Improper Input Validation in EnvoyExtensionPolicy Lua Allows Secret DisclosureGHSA-wcrf-9vrr-854f
CRITICALGHSA-wcrf-9vrr-854f is a critical-severity (CVSS 9.1) Improper Input Validation vulnerability in github.com/envoyproxy/gateway. A fix is available for github.com/envoyproxy/gateway — see the affected versions and patch details below.
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-wcrf-9vrr-854f.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
GHSA-wcrf-9vrr-854f by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 394,415 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
github.com/envoyproxy/gateway🐹github.com/envoyproxy/gatewayReal-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
The to_absolute_normalized_path function (security.lua:28-43) does not collapse redundant path separators (// → /). On Linux, //etc/passwd is equivalent to /etc/passwd (POSIX path semantics), but is_critical_path fails to match the double-slash variant because //etc/passwd does not start with /etc/.
This allows Lua code submitted as an EnvoyExtensionPolicy to read arbitrary files from the gateway controller pod's filesystem during Strict validation (the default), including:
/etc/passwd- Kubernetes SA tokens via
//var/run/secrets/kubernetes.io/serviceaccount/token - TLS certificates via
//certs/... - Process environment via
//proc/self/environ
These credentials can be used to read sensitive information from the K8s API Server or from the Gateway XDS server.
Patches
This has been patched in versions >= v1.7.4 and v1.8.1
- Collapse redundant path separators (
//to/) so double-slash variants like//etc/passwdand//var/run/secrets/...are matched by the critical-path check. - Rewrite the traversal check to reject any
.or..segment in any position and across both separator styles (catches/etc/./passwd,./etc/passwd,/etc/.).
Workarounds
Please refer to the Warning section in Lua docs for measures to reduce risk.
Credits
Envoy Gateway thanks @dashingDragon and @Donjon-Cerberus for reporting this issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/envoyproxy/gateway | ≥ 1.8.0-rc.0&&< 1.8.1 | 1.8.1go get github.com/envoyproxy/gateway@v1.8.1 |
| 🐹Go | github.com/envoyproxy/gateway | all versions | 1.7.4go get github.com/envoyproxy/gateway@v1.7.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/envoyproxy/gateway, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/envoyproxy/gateway to 1.8.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-wcrf-9vrr-854f 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.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
A critical flaw was found in Envoy Gateway, an open source project for managing Envoy Proxy as a standalone or Kubernetes-based application gateway. The to_absolute_normalized_path function in internal/gatewayapi/luavalidator/security.lua does not collapse redundant path separators before is_critical_path evaluates…
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.Source: Red Hat security advisory for GHSA-wcrf-9vrr-854f (CC BY 4.0)
Frequently Asked Questions
Is GHSA-wcrf-9vrr-854f in your dependencies?
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