# CVE-2026-88004: Traefik entrypoint header-name sanitization bypassed via request trailers

> Attackers can bypass header sanitization in Traefik by using HTTP trailers, potentially spoofing identity or routing data to backend services.

- **Severity:** High 7.0 (`CVSS:4.0/AV:N/AC:H/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:** 10 Sep 2026
- **Updated:** 10 Sep 2026
- **Also known as:** ECHO-15c1-824f-cb33, GHSA-v67p-phpq-fc8x, GO-2026-6467, MINI-5q89-8744-cwx7, MINI-xc5m-jqv5-mq57

## What is CVE-2026-88004?

CVE-2026-88004 is a high-severity vulnerability in Traefik Traefik, published on 10 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Traefik is an open source HTTP reverse proxy and load balancer. From 3.2.0 until 3.7.13, Traefik entrypoint defenses aliasHeadersStrategy, underscoreHeadersStrategy, and forwardedHeaders inspect req.Header but not req.Trailer, allowing an unauthenticated client to submit an aliasing or trusted header name in an HTTP/1.1 chunked trailer or an HTTP/2 trailer. When the retry or buffering middleware reads the body before the reverse proxy clones the request, the attacker-controlled trailer value reaches a backend that merges trailers into the header namespace, bypassing the documented delete or reject behavior and potentially spoofing identity or forwarded routing data. This issue is fixed in 3.7.13.

Weakness: CWE-807 (Reliance on Untrusted Inputs in a Security Decision), CWE-436 (Interpretation Conflict)

## Which versions are affected by CVE-2026-88004?

5 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 | From 3.2.0 | 3.7.13 |
| `github.com/traefik/traefik/v3` | Go | From 3.2.0 | 3.7.13 |
| `github.com/traefik/traefik/v3` | Go | From 3.2.0 | 3.7.13 |
| `github.com/traefik/traefik` | Go | All versions | None |
| `github.com/traefik/traefik/v2` | Go | All versions | None |

Products: Traefik Traefik.

## How do I fix CVE-2026-88004?

Upgrade github.com/traefik/traefik/v3 to 3.7.13 or later.

## Is CVE-2026-88004 being exploited?

There is no known exploitation of CVE-2026-88004 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-2026-88004 and fix it if it is affected.

What it is: CVE-2026-88004 is a high-severity vulnerability in Traefik Traefik, published on 10 Sep 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-2026-88004 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/traefik/traefik/v3 (Go): affected from 3.2.0; fixed in 3.7.13
- github.com/traefik/traefik/v3 (Go): affected from 3.2.0; fixed in 3.7.13
- github.com/traefik/traefik/v3 (Go): affected from 3.2.0; fixed in 3.7.13
- github.com/traefik/traefik (Go): affected all versions; no fix listed
- github.com/traefik/traefik/v2 (Go): affected all versions; no fix listed

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-2026-88004/ (Markdown: https://insights.sbomify.com/CVE-2026-88004/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-88004
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-88004
- OSV: https://osv.dev/vulnerability/CVE-2026-88004

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-88004/
Summaries are generated and may contain mistakes; the official description above is the record.