Authentication Bypass in github.com/traefik/traefik/v3 (CVE-2026-71326)
Summary
Authentication bypass in github.com/traefik/traefik/v3 (CVE-2026-71326). Risk of unauthorized operations or information disclosure. Exploitable via GET /api/http/middlewares/{id}. Mitigation: upgrade to 3.7.10 or later.
Original description
The description as published by the source.
Summary
There is a low severity vulnerability in Traefik's BasicAuth middleware. Concurrent password verifications are deduplicated through a singleflight group whose key was the delimiter-free concatenation of the submitted password and the stored secret, so a request carrying an unconfigured username — whose secret is empty — can produce the same key as a configured user's valid request and receive that request's successful result. Exploitation requires the attacker to already hold a valid credential and to read the stored password hash, which is only reachable through paths that are themselves privileged: the API is documented as admin-only, the Kubernetes path requires read access to the Secret, and the Docker path requires access to the socket. The key now encodes the password length as a prefix, so distinct (password, secret) pairs can no longer collide. Only the v3.6 line from v3.6.11 onwards and the v3.7 line are affected; earlier v3 releases and the v2 line do not carry the vulnerable deduplication path.
Patches
- https://github.com/traefik/traefik/releases/tag/v3.6.25
- https://github.com/traefik/traefik/releases/tag/v3.7.10
For more information
If you have any questions or comments about this advisory, please open an issue.
Original Description
Summary
Traefik's BasicAuth middleware deduplicates concurrent password checks with a
singleflight.Group. Its key is the delimiter-free concatenation
`pa…
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-71326 has been found in github.com/traefik/traefik/v3.
Attackers can target a specific entry point like GET /api/http/middlewares/{id} over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 3.8/10.
What to do: upgrade github.com/traefik/traefik/v3 to 3.7.10 or later.
If unsure, ask your IT team or search "github.com/traefik/traefik/v3 CVE-2026-71326" on the vendor's site.
CVE-2026-71326 (github.com/traefik/traefik/v3) — CWE-287 / CVSS v3 3.8
Attack vector: remote (network-reachable) / no user interaction
Attack surface: GET /api/http/middlewares/{id} / singleflight.Group / URL.User / headerField
Patched: 3.7.10 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Authentication bypass (CWE-287) exists in github.com/traefik/traefik/v3. Attackers reach the vulnerable code path via GET /api/http/middlewares/{id}.
Check the vendor advisory for the affected versions of github.com/traefik/traefik/v3. Attack surface: GET /api/http/middlewares/{id} / singleflight.Group / URL.User / headerField.
Severity: Low (CVSS 3.8/10). Risk of unauthorized operations or information disclosure.
Update to 3.7.10.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual GET /api/http/middlewares/{id} requests with malformed payloads or SQL meta-characters. Run grep -r 'github.com/traefik/traefik/v3' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'github.com/traefik/traefik/v3' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
github.com/traefik/traefik/v3を grep し、稼働しているサービス・バージョンを把握する。 -
2Hunt for indicators of compromise detect
grep 'GET /api/http/middlewares/{id}' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'アクセスログで
GET /api/http/middlewares/{id}への異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。 -
3Apply patch patch
Upgrade github.com/traefik/traefik/v3 to 3.7.10ステージング環境で 3.7.10 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスと、Step 2 で見つけた異常検知の続報チェックを含めること。
-
4Post-deployment verification verify
Replay attack against GET /api/http/middlewares/{id} on staging to confirm patch closes the vectorパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番では Step 2 と同じログクエリでアラート再発が無いか継続監視。