CVE-2026-54763
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedTraefik is an HTTP reverse proxy and load balancer. Prior to v2.11.51, v3.6.22, and v3.7.6, Traefik's BasicAuth, DigestAuth, and ForwardAuth middlewares strip canonical-cased spoofed identity headers before writing Traefik's own value, but do not account for underscore-variant header names, which many backends normalize identically to dashed forms. An attacker able to reach a protected route can inject an underscore-variant header that survives Traefik's stripping and reaches the backend alongside, or on the unauthenticated ForwardAuth authResponseHeaders path instead of, the value Traefik intended to set, spoofing identity or authorization context. This issue is fixed in versions v2.11.51, v3.6.22, and v3.7.6.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceTraefik's BasicAuth, DigestAuth, and ForwardAuth middlewares fail to strip underscore-variant spoofed identity headers (e.g., X-Forwarded-User vs X_Forwarded_User). Attackers can inject underscore-variant headers that bypass Traefik's header stripping logic and reach backends alongside or instead of Traefik's intended values, enabling identity/authorization context spoofing.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 2.11.51>= 3.0.0, < 3.6.22>= 3.7.0, < 3.7.6CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Changed
- Confidentiality
- High
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify installed Traefik versionRun `traefik --version` or check the container image/tag version deployed in your environmentAffected if The version is < 2.11.51, or >= 3.0.0 and < 3.6.22, or >= 3.7.0 and < 3.7.6
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Locate active middleware configurationsReview your Traefik configuration files (YAML, TOML, or dynamic configuration) and identify any middleware definitions using BasicAuth, DigestAuth, or ForwardAuth typesAffected if Any of these three authentication middlewares are configured and active in your routing setup
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Verify header forwarding behaviorInspect the ForwardAuth middleware configuration to identify which headers are passed to backends (commonly X-Forwarded-User or similar identity headers)Affected if ForwardAuth is configured to forward user identity headers to backends without additional validation of header names
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Check backend application header trustExamine backend application configurations or code to determine if they trust incoming headers with underscore variants (e.g., X_Forwarded_User, X_Forwarded_Email) in addition to hyphenated formsAffected if Backends accept or process underscore-variant identity headers without rejecting or stripping them
You are affected if your Traefik version falls within the vulnerable ranges AND you use BasicAuth, DigestAuth, or ForwardAuth middlewares that forward identity headers to backends that may trust underscore-variant headers.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped2.11.513.6.223.7.6
Upgrade Traefik to v2.11.51, v3.6.22, or v3.7.6 or later. Verify that backend applications relying on identity headers are not inadvertently trusting underscore-variant headers that were previously ignored.
v2.11.51 (for v2.x users) or v3.6.22/v3.7.6 (for v3.x users)
- 1. Identify the currently installed Traefik version by running `traefik --version` or checking the deployment manifests
- 2. Determine which major version line (v2.x or v3.x) is currently in use
- 3. For Traefik v2.x users: Upgrade to v2.11.51 or later
- 4. For Traefik v3.0.0-3.6.x users: Upgrade to v3.6.22 or later
- 5. For Traefik v3.7.0-3.7.5 users: Upgrade to v3.7.6
- 6. Verify the upgrade was successful by running `traefik --version` and confirming the version number matches or exceeds the appropriate fixed release
- 7. Test that authentication middlewares (BasicAuth, DigestAuth, ForwardAuth) function correctly with the new version
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-54763 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-54763 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
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- Version or environment caveats, and links to real fixes
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