# CVE-2026-71326: Traefik: BasicAuth singleflight key collision allows authenticated identity spoofing

> Traefik's BasicAuth middleware allows authenticated users to spoof identities due to a singleflight key collision, enabling unauthorized access when headerField is trusted.

- **Severity:** Low 2.1 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 Aug 2026
- **Updated:** 8 Aug 2026
- **Also known as:** GHSA-6765-c87h-8mrf, GO-2026-6204, MINI-j9fm-fh53-7w2f, MINI-pfw6-6q2j-fxq6, MINI-rr56-79fm-7x6w

## What is CVE-2026-71326?

CVE-2026-71326 is a low-severity authentication bypass vulnerability in Traefik Traefik, published on 6 Aug 2026. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

Traefik is an open source HTTP reverse proxy and load balancer. From 3.6.11 until 3.6.25 and 3.7.10, Traefik's BasicAuth middleware in pkg/middlewares/auth/basic_auth.go deduplicates concurrent password checks with a singleflight key built from the delimiter-free concatenation of password and secret, allowing an attacker who has a valid credential and the stored hash to authenticate as an unconfigured username when headerField trusts the forwarded identity. This issue is fixed in 3.6.25 and 3.7.10.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2026-71326?

7 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 3.6.11 | 3.6.25, 3.7.10 |
| `github.com/traefik/traefik/v3` | Go | From 3.6.11 | 3.6.25 |
| `github.com/traefik/traefik/v3` | Go | From 3.6.11 | 3.6.25 |
| `github.com/traefik/traefik/v3` | Go | From 3.7.0 | 3.7.10 |
| `github.com/traefik/traefik/v3` | Go | From 3.7.0 | 3.7.10 |
| `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-2026-71326?

Upgrade github.com/traefik/traefik/v3 to a fixed version for your release line: 3.6.25 or 3.7.10.

## Is CVE-2026-71326 being exploited?

There is no known exploitation of CVE-2026-71326 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-2026-71326 and fix it if it is affected.

What it is: CVE-2026-71326 is a low-severity authentication bypass vulnerability in Traefik Traefik, published on 6 Aug 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-71326 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/traefik/traefik/v3 (Go): affected from 3.6.11; fixed in 3.6.25, 3.7.10
- github.com/traefik/traefik/v3 (Go): affected from 3.6.11; fixed in 3.6.25
- github.com/traefik/traefik/v3 (Go): affected from 3.6.11; fixed in 3.6.25
- github.com/traefik/traefik/v3 (Go): affected from 3.7.0; fixed in 3.7.10
- github.com/traefik/traefik/v3 (Go): affected from 3.7.0; fixed in 3.7.10
- 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-2026-71326/ (Markdown: https://insights.sbomify.com/CVE-2026-71326/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-71326
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-71326
- OSV: https://osv.dev/vulnerability/CVE-2026-71326

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-71326/
Summaries are generated and may contain mistakes; the official description above is the record.