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

Quick assessment

Affected
traefik traefik
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Traefik 是一个开源的 HTTP 反向代理和负载均衡器。在 2.11.56 之前，以及从 3.0.0 到 3.7.12 版本，客户端提供的点分头（如 X.Authenticated.User）能够穿透 ForwardAuth 替换和 underscoreHeadersStrategy。这是因为 Go 语言将 视为与 不同的头部名称，而容易进行头部规范化处理的 CGI、WSGI、PHP 和 NGINX 后端会将这两种名称归一化为同一个头部。因此，后端可能直接消费客户端提供的头部值，而非 Traefik 所断言的

CVSS 5.3 · Medium
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I. Basic Information for CVE-2026-88011

Vulnerability Information
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Vulnerability Title
Traefik: ForwardAuth identity spoofing via dot-form header alias
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
使用欺骗进行的认证绕过
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
traefik traefik < 2.11.56 -

II. Public POCs for CVE-2026-88011

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III. Intelligence Information for CVE-2026-88011

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Vendor Advisories for CVE-2026-88011 (1)

Other References for CVE-2026-88011 (3)

Same Patch Batch · traefik · 2026-09-10 · 9 CVEs total

CVE-2026-88877 9.8 CRITICAL Traefik v3.7.0 Authentication Bypass via from-to-www-redirect
CVE-2026-88007 9.1 CRITICAL Traefik HTTP/3 Backend NTLM Connection Reuse
CVE-2026-88009 8.8 HIGH Traefik: Rootless HTTP/1 request-target routes as "/" but is forwarded verbatim, bypassing
CVE-2026-88004 7.0 HIGH Traefik entrypoint header-name sanitization bypassed via request trailers
CVE-2026-88008 7.0 HIGH Traefik: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
CVE-2026-88879 5.3 MEDIUM Traefik before v2.11.56 Identity Spoofing via Header Alias
CVE-2026-88878 5.3 MEDIUM Traefik v2.8.2 through v3.6 HTTP/3 Timeout Bypass
CVE-2026-88012 5.3 MEDIUM Traefik: respondingTimeouts.readTimeout is not applied to HTTP/3, leaving slow-body upload

IV. Related Vulnerabilities

Same product: traefik
Same vendor: traefik
Same weakness: CWE-290

V. Comments for CVE-2026-88011

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