CVE-2026-41246: Contour: Lua code injection via Cookie Path Rewrite Policy

Severity: high (CVSS 8.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-04-23 · updated 2026-10-26
Weakness: CWE-94

Description

Contour is a Kubernetes ingress controller using Envoy proxy. From v1.19.0 to before v1.33.4, v1.32.5, and v1.31.6, 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 spec.routes[].cookieRewritePolicies[].pathRewrite.value or spec.routes[].services[].cookieRewritePolicies[].pathRewrite.value that results in arbitrary code execution in the Envoy proxy. 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 or cause denial of service for other tenants sharing the Envoy instance. This vulnerability is fixed in v1.33.4, v1.32.5, and v1.31.6.

Affected products

projectcontour contour: from 1.19.0 before 1.31.6; from 1.32.0 before 1.32.5; from 1.33.0 before 1.33.4 — fixed in 1.31.6, 1.32.5, 1.33.4

How to fix

Upgrade to a fixed version: projectcontour contour 1.31.6, 1.32.5, 1.33.4. Check the vendor advisory for mitigations.

References

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