# CVE-2026-54763: Traefik: headerField underscore-variant identity spoofing in BasicAuth / DigestAuth / ForwardAuth

> Attackers can spoof identity headers via underscore variants in Traefik's auth middlewares, bypassing authentication controls to access protected routes.

- **Severity:** High 7.8 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 Jul 2026
- **Updated:** 8 Jul 2026
- **Also known as:** GHSA-x677-9fxg-v5c5, GO-2026-6211, MINI-5xmp-q2qc-2h34, MINI-p6f8-r3f5-4pfp, MINI-q6mh-hqhr-h6cp

## What is CVE-2026-54763?

CVE-2026-54763 is a high-severity authentication bypass vulnerability in Traefik Traefik, published on 6 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-345 (Insufficient Verification of Data Authenticity), CWE-290 (Authentication Bypass by Spoofing), CWE-178 (Improper Handling of Case Sensitivity)

## Which versions are affected by CVE-2026-54763?

9 open source packages ship an affected version, including github.com/traefik/traefik/v3, github.com/traefik/traefik and github.com/traefik/traefik/v2. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/traefik/traefik/v3` | Go | All versions | 3.6.22, 3.7.6 |
| `github.com/traefik/traefik/v3` | Go | All versions | 3.6.22 |
| `github.com/traefik/traefik/v3` | Go | All versions | 3.6.22 |
| `github.com/traefik/traefik/v3` | Go | From 3.7.0 | 3.7.6 |
| `github.com/traefik/traefik/v3` | Go | From 3.7.0 | 3.7.6 |
| `github.com/traefik/traefik` | Go | All versions | None |
| `github.com/traefik/traefik/v2` | Go | All versions | 2.11.51 |
| `github.com/traefik/traefik/v2` | Go | All versions | 2.11.51 |
| `github.com/traefik/traefik/v2` | Go | All versions | 2.11.51 |

Products: Traefik Traefik.

## How do I fix CVE-2026-54763?

Upgrade github.com/traefik/traefik/v3 to a fixed version for your release line: 3.6.22 or 3.7.6.

## Is CVE-2026-54763 being exploited?

There is no known exploitation of CVE-2026-54763 in the wild and no public exploit code.

## Other vulnerabilities in Traefik Traefik

- [CVE-2024-45410](https://insights.sbomify.com/CVE-2024-45410/): HTTP client can remove the X-Forwarded headers in Traefik (critical 9.8)
- [CVE-2026-88877](https://insights.sbomify.com/CVE-2026-88877/): Traefik v3.7.0 Authentication Bypass via from-to-www-redirect (critical 9.3)
- [CVE-2026-85595](https://insights.sbomify.com/CVE-2026-85595/): Traefik before v2.11.55 and v3.0.0 through v3.7.10 Authentication Bypass via digestAuth (critical 9.3)
- [CVE-2026-88007](https://insights.sbomify.com/CVE-2026-88007/): Traefik HTTP/3 Backend NTLM Connection Reuse (critical 9.1)
- [CVE-2026-88009](https://insights.sbomify.com/CVE-2026-88009/): Traefik: Rootless HTTP/1 request-target routes as "/" but is forwarded verbatim, bypassing path-scoped routing, middleware guards and access logging (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-54763 and fix it if it is affected.

What it is: CVE-2026-54763 is a high-severity authentication bypass vulnerability in Traefik Traefik, published on 6 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-54763 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/traefik/traefik/v3 (Go): affected all versions; fixed in 3.6.22, 3.7.6
- github.com/traefik/traefik/v3 (Go): affected all versions; fixed in 3.6.22
- github.com/traefik/traefik/v3 (Go): affected all versions; fixed in 3.6.22
- github.com/traefik/traefik/v3 (Go): affected from 3.7.0; fixed in 3.7.6
- github.com/traefik/traefik/v3 (Go): affected from 3.7.0; fixed in 3.7.6
- github.com/traefik/traefik (Go): affected all versions; no fix listed
- github.com/traefik/traefik/v2 (Go): affected all versions; fixed in 2.11.51
- github.com/traefik/traefik/v2 (Go): affected all versions; fixed in 2.11.51
- github.com/traefik/traefik/v2 (Go): affected all versions; fixed in 2.11.51

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-54763/ (Markdown: https://insights.sbomify.com/CVE-2026-54763/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-54763
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-54763
- OSV: https://osv.dev/vulnerability/CVE-2026-54763

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-54763/
Summaries are generated and may contain mistakes; the official description above is the record.