{
  "canonical_id": "traefik--CVE-2026-29054",
  "system_id": "traefik",
  "display_name": "Traefik",
  "category": "servers",
  "advisory_mode": "server",
  "title": "traefik CVE-2024-45410 fix bypass: lowercase `Connection` tokens can delete traefik-managed forwarded identity headers (for example, `X-Real-Ip`)",
  "summary": "## Impact\n\nThere is a potential vulnerability in Traefik managing the `Connection` header with `X-Forwarded` headers.\n\nWhen Traefik processes HTTP/1.1 requests, the protection put in place to prevent the removal of Traefik-managed `X-Forwarded` headers (such as `X-Real-Ip`, `X-Forwarded-Host`, `X-Forwarded-Port`, etc.) via the `Connection` header does not handle case sensitivity correctly. The `Connection` tokens are compared case-sensitively against the protected header names, but the actual header deletion operates case-insensitively. As a result, a remote unauthenticated client can use lowercase `Connection` tokens (e.g. `Connection: x-real-ip`) to bypass the protection and trigger the removal of Traefik-managed forwarded identity headers.\n\nThis is a bypass of the fix for [CVE-2024-45410](https://github.com/traefik/traefik/security/advisories/GHSA-62c8-mh53-4cqv).\n\nDepending on the deployment, the impact may be higher if downstream services rely on these headers (such as `X-Real-Ip` or `X-Forwarded-*`) for authentication, authorization, routing, or scheme decisions.\n\n## Patches\n\n- https://github.com/traefik/traefik/releases/tag/v2.11.38\n- https://github.com/traefik/traefik/releases/tag/v3.6.9\n\n## Workarounds\n\nNo workaround available.\n\n## For more information\n\nIf there are any questions or comments about this advisory, please [open an issue](https://github.com/traefik/traefik/issues).\n\n---\n\n<details>\n<summary>Original Description</summary>\n\nTraefik's XForwarded middleware (removeConnectionHeaders) tries to prevent clients from using the Connection header to strip trusted X-Forwarded-* headers, but the protection compares the Connection tokens case-sensitively while the deletion is case-insensitive.\n\nAs a result, a remote unauthenticated client can send a lowercase token like Connection: x-real-ip and still trigger deletion of traefik-managed X-Real-Ip (and similarly named headers in the managed list).\n\nThis can cause downstream routing, scheme, and header-based authn/authz decisions to be evaluated with missing trusted forwarding identity headers.\n\n### Severity\n\nCRITICAL\n\nRationale: the PoC demonstrates an end-to-end access control bypass pattern when a downstream service uses proxy-provided identity headers (for example, X-Real-Ip) for IP allowlists or trust decisions. A remote unauthenticated client can strip the traefik-managed identity header via a lowercase Connection token, causing the downstream service to evaluate the request without the expected header signal.\n\n### Relevant Links\n\n- Repository: https://github.com/traefik/traefik\n- Pinned commit: a4a91344edcdd6276c1b766ca19ee3f0e346480f\n- Callsite (pinned): https://github.com/traefik/traefik/blob/a4a91344edcdd6276c1b766ca19ee3f0e346480f/pkg/middlewares/forwardedheaders/forwarded_header.go#L225\n\n### Vulnerability Details\n\n#### Root Cause\n\nremoveConnectionHeaders uses a case-sensitive membership check for protected header names when inspecting Connection tokens, but it deletes headers via net/http which treats header names case-insensitively. A lowercase token bypasses the protection check and still triggers deletion.\n\n#### Attacker Control / Attack Path\n\nRemote unauthenticated HTTP client (untrusted IP) sends Connection: x-real-ip, and Traefik deletes the generated X-Real-Ip header.\n\n### Proof of Concept\n\nThe attached poc.zip contains a deterministic, make-based integration PoC with a canonical run and a negative control.\n\nCanonical (vulnerable):\n\n    unzip poc.zip -d poc\n    cd poc\n    make test\n\nOutput contains:\n\n    [CALLSITE_HIT]: pkg/middlewares/forwardedheaders/forwarded_header.go:225\n    [PROOF_MARKER]: downstream_admin_bypass=1 x_real_ip_present=0\n\nControl (same env, no lowercase token):\n\n    unzip poc.zip -d poc\n    cd poc\n    make test\n\nOutput contains:\n\n    [CALLSITE_HIT]: pkg/middlewares/forwardedheaders/forwarded_header.go:225\n    [NC_MARKER]: downstream_admin_bypass=0 x_real_ip_present=1\n\nExpected: Connection tokens are handled case-insensitively and protected identity headers (for example, X-Real-Ip and X-Forwarded-*) are not deleted due to client-supplied Connection options (regardless of token casing).\n\nActual: Lowercase Connection tokens bypass the protection check and still trigger deletion of traefik-managed identity headers (for example, X-Real-Ip).\n\n### Recommended Fix\n\n- Case-fold (or otherwise canonicalize) Connection header tokens before comparing them against protected header names.\n- Add a regression test covering lowercase tokens (for example, Connection: x-real-ip).\n\nFix accepted when: a request with Connection: x-real-ip does not cause deletion of traefik-managed X-Real-Ip, and a regression test covers this behavior.\n\n</details>",
  "published_at": "2026-03-04T21:19:08Z",
  "updated_at": "2026-03-05T22:46:31.066201Z",
  "severity": "low",
  "cvss_score": 3.1,
  "exploit_status": "unknown",
  "source_confidence": "official",
  "official_source_url": "https://github.com/traefik/traefik/security/advisories/GHSA-92mv-8f8w-wq52",
  "secondary_source_urls": [
    "https://nvd.nist.gov/vuln/detail/CVE-2026-29054",
    "https://github.com/traefik/traefik",
    "https://github.com/traefik/traefik/releases/tag/v2.11.38",
    "https://github.com/traefik/traefik/releases/tag/v3.6.9"
  ],
  "aliases": [
    "CVE-2026-29054",
    "GHSA-92mv-8f8w-wq52"
  ],
  "cve_ids": [
    "CVE-2026-29054"
  ],
  "ghsa_ids": [
    "GHSA-92mv-8f8w-wq52"
  ],
  "osv_ids": [
    "GHSA-92mv-8f8w-wq52"
  ],
  "affected_versions": [
    "introduced=2.11.9, fixed<2.11.38",
    "introduced=3.1.3, fixed<3.6.9"
  ],
  "fixed_versions": [
    "2.11.38",
    "3.6.9"
  ],
  "package_name": "github.com/traefik/traefik/v3",
  "render_markdown": false,
  "case_path": null,
  "secure_code_topics": [
    "proxy-trust-boundary",
    "request-smuggling-boundary",
    "token-cookie-storage",
    "authz-server-side-recheck",
    "dependency-upgrade-policy"
  ],
  "status": "generated",
  "triage_reasons": [],
  "entity_refs": [
    {
      "entity_id": "traefik",
      "entity_type": "system",
      "relation": "root-system",
      "root_system_id": "traefik",
      "official": true
    },
    {
      "entity_id": "traefik--repo--github-com-traefik-traefik-v3",
      "entity_type": "repo",
      "relation": "affected-component",
      "root_system_id": "traefik",
      "official": false
    }
  ],
  "affected_components": [
    {
      "name": "traefik / traefik / v3",
      "entity_id": "traefik--repo--github-com-traefik-traefik-v3",
      "scope": "repo",
      "package_name": "github.com/traefik/traefik/v3",
      "official": false
    }
  ],
  "affected_version_ranges": [
    "introduced=2.11.9, fixed<2.11.38",
    "introduced=3.1.3, fixed<3.6.9"
  ],
  "fixed_version_ranges": [
    "2.11.38",
    "3.6.9"
  ],
  "introduced_version": "introduced=3.1.3, fixed<3.6.9",
  "patched_version": "2.11.38",
  "version_evidence_sources": [
    "https://github.com/traefik/traefik/security/advisories/GHSA-92mv-8f8w-wq52",
    "https://nvd.nist.gov/vuln/detail/CVE-2026-29054",
    "https://github.com/traefik/traefik",
    "https://github.com/traefik/traefik/releases/tag/v2.11.38",
    "https://github.com/traefik/traefik/releases/tag/v3.6.9"
  ],
  "advisory_scope": "repo",
  "version_confidence": "high",
  "version_gap_reason": "",
  "version_resolution_needed": false,
  "workflow": {
    "workflow_id": "traefik--CVE-2026-29054--workflow",
    "vuln_family": "authz-bypass",
    "entry_surface": "privileged-route-or-object-reference",
    "preconditions": [
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    "required_role": "cross-tenant-or-low-privileged-user",
    "affected_version_assertion": [
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    "request_or_ui_path": [
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      "/api/private/*",
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    "browser_evidence_points": [
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      "console\u3001network \u4e0e response metadata \u4e2d\u7684\u5f02\u5e38\u4fe1\u53f7"
    ],
    "db_or_fs_evidence_points": [
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    "detection_signals": [
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    "patch_validation_steps": [
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    "review_state": "ready"
  },
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  "last_run_id": null,
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    "present": false,
    "refs": []
  },
  "repro_profile_id": "authz-bypass-generic",
  "artifact_mode": "synthetic",
  "blocked_reason": null,
  "metadata": {
    "source_names": [
      "OSV Traefik"
    ],
    "source_kinds": [
      "osv-batch"
    ],
    "candidate_count": 1,
    "entity_ref_count": 2,
    "advisory_scope": "repo",
    "version_confidence": "high",
    "workflow_id": "traefik--CVE-2026-29054--workflow"
  }
}