GHSA-X4MJ-7F9G-29H4

Vulnerability from github – Published: 2026-04-24 15:19 – Updated: 2026-04-24 15:19
VLAI?
Summary
Contour has Lua code injection via Cookie Path Rewrite Policy
Details

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.value
  • spec.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/template is 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.

Severity ?
8.1 (High)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/projectcontour/contour"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.19.0"
            },
            {
              "fixed": "1.31.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/projectcontour/contour"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.32.0"
            },
            {
              "fixed": "1.32.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/projectcontour/contour"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.33.0"
            },
            {
              "fixed": "1.33.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-41246"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-94"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-24T15:19:49Z",
    "nvd_published_at": "2026-04-23T19:17:29Z",
    "severity": "HIGH"
  },
  "details": "### Impact\n\nContour\u0027s [Cookie Rewriting](https://projectcontour.io/docs/1.33/config/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:\n\n- `spec.routes[].cookieRewritePolicies[].pathRewrite.value`\n- `spec.routes[].services[].cookieRewritePolicies[].pathRewrite.value`\n\nThe cookie rewriting feature is internally implemented using Envoy\u0027s [HTTP Lua filter](https://www.envoyproxy.io/docs/envoy/latest/configuration/http/http_filters/lua_filter). User-controlled values are interpolated into Lua source code using Go `text/template` without sufficient sanitization.\n\nThe injected code only executes when processing traffic on the attacker\u0027s own route, which they already control. However, since Envoy runs as shared infrastructure, the injected code can also:\n\n- Read Envoy\u0027s 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.\n- Cause denial of service for other tenants sharing the Envoy instance.\n\nOther use cases of Lua filter are not vulnerable.\n\n### Patches\n\nThe fix is available in Contour [v1.33.4](https://github.com/projectcontour/contour/releases/tag/v1.33.4), [v1.32.5](https://github.com/projectcontour/contour/releases/tag/v1.32.5), and [v1.31.6](https://github.com/projectcontour/contour/releases/tag/v1.31.6).\n\n- v1.33.4: User-provided values are no longer interpolated into Lua code. Use of `text/template` is removed. Requires Envoy 1.35.0 or later.\n- v1.32.5, v1.31.6: User-provided values are escaped before interpolation into Lua code.\n\n### Workarounds\n\nThere are no workarounds. Users should upgrade to a patched version.",
  "id": "GHSA-x4mj-7f9g-29h4",
  "modified": "2026-04-24T15:19:49Z",
  "published": "2026-04-24T15:19:49Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/projectcontour/contour/security/advisories/GHSA-x4mj-7f9g-29h4"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-41246"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/projectcontour/contour"
    },
    {
      "type": "WEB",
      "url": "https://github.com/projectcontour/contour/releases/tag/v1.31.6"
    },
    {
      "type": "WEB",
      "url": "https://github.com/projectcontour/contour/releases/tag/v1.32.5"
    },
    {
      "type": "WEB",
      "url": "https://github.com/projectcontour/contour/releases/tag/v1.33.4"
    },
    {
      "type": "WEB",
      "url": "https://projectcontour.io/docs/1.33/config/cookie-rewriting"
    },
    {
      "type": "WEB",
      "url": "https://www.envoyproxy.io/docs/envoy/latest/configuration/http/http_filters/lua_filter"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Contour has Lua code injection via Cookie Path Rewrite Policy"
}


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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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