# CVE-2026-88011: Traefik: ForwardAuth identity spoofing via dot-form header alias

> Attackers can spoof identity headers in Traefik ForwardAuth setups if alias protection is disabled, allowing unauthorized access to backends.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 10 Sep 2026
- **Updated:** 15 Sep 2026
- **Also known as:** ECHO-623a-37ca-7a37, MINI-3cm7-7494-jx7m, MINI-gqhr-g88j-q3jr, MINI-w2qc-rwf4-r9h4

## What is CVE-2026-88011?

CVE-2026-88011 is a medium-severity authentication bypass vulnerability in Traefik Traefik, published on 10 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Traefik is an open source HTTP reverse proxy and load balancer. Prior to 2.11.56, and from 3.0.0 until 3.7.12, a client-supplied dot-form header such as X.Authenticated.User survives ForwardAuth replacement and underscoreHeadersStrategy because Go treats it as distinct from X-Authenticated-User while normalization-prone CGI, WSGI, PHP, and NGINX backends collapse both names. A backend can consequently consume the client value instead of the identity Traefik asserted, allowing identity spoofing for any header managed by Traefik. The aliasHeadersStrategy protection is disabled by default and must be configured as delete or reject. The mitigation is available in 2.11.56 and 3.7.12.

Weakness: CWE-290 (Authentication Bypass by Spoofing)

## Which versions are affected by CVE-2026-88011?

It affects 1 product.


Products: Traefik Traefik.

## How do I fix CVE-2026-88011?

Upgrade to a fixed version.

## Is CVE-2026-88011 being exploited?

There is no known exploitation of CVE-2026-88011 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-2026-88011 and fix it if it is affected.

What it is: CVE-2026-88011 is a medium-severity authentication bypass vulnerability in Traefik Traefik, published on 10 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-88011 in the wild and no public exploit code.

Affected product: Traefik Traefik. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-88011/ (Markdown: https://insights.sbomify.com/CVE-2026-88011/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-88011
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-88011
- OSV: https://osv.dev/vulnerability/CVE-2026-88011

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-88011/
Summaries are generated and may contain mistakes; the official description above is the record.