CVE-2026-54763
Fix: traefik/traefik@108a526CVE-2026-54763 is a CWE-178 vulnerability in github.com/traefik/traefik/v2. O3 Security confirms whether CVE-2026-54763 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Traefik: headerField underscore-variant identity spoofing in BasicAuth / DigestAuth / ForwardAuth
Real-World Exposure
github.com/traefik/traefik/v2🐹github.com/traefik/traefik/v3🐹github.com/traefik/traefik/v3Real-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
Traefik 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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/traefik/traefik/v2 | all versions | 2.11.51 |
| 🐹Go | github.com/traefik/traefik/v3 | all versions | 3.6.22 |
| 🐹Go | github.com/traefik/traefik/v3 | ≥ 3.7.0&&< 3.7.6 | 3.7.6 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/traefik/traefik/v2. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/traefik/traefik/v2 to 2.11.51 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-54763 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.
How O3 protects you
O3 pinpoints whether CVE-2026-54763 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-54763. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-54763 in your dependencies?
O3 detects CVE-2026-54763 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.