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CVE-2026-88877— Traefik v3.7.0 Authentication Bypass via from-to-www-redirect

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 HTTP 反向代理和负载均衡器。在 v3.7.0 到 v3.7.11 版本中，Kubernetes ingress-nginx 提供者对同时带有认证注解和 注解的 Ingress 资源处理不当。对于这类 Ingress，该提供者会创建一个额外的“兄弟”路由器，该路由器仅根据主机名进行匹配，仅携带 中间件，并且仍然指向父路由器的受保护后端服务。 由于 并非终止型处理器（terminal handler），当请求的 URL 不匹配其重定向模式时，请求会被转发至后端服务。同时，因为该重定向模式仅接

CVSS 9.8 · Critical
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I. Basic Information for CVE-2026-88877

Vulnerability Information
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Vulnerability Title
Traefik v3.7.0 Authentication Bypass via from-to-www-redirect
Source: CVE Program / CVE List V5
Vulnerability Description
Traefik is a HTTP reverse proxy and load balancer. In versions >= v3.7.0 and <= v3.7.11, the Kubernetes ingress-nginx provider mishandles Ingresses that carry both an authentication annotation and the nginx.ingress.kubernetes.io/from-to-www-redirect annotation. For such Ingresses the provider creates an additional 'sibling' router that matches on the host alone, carries only the RedirectRegex middleware, and still points at the parent router's protected backend service. Because RedirectRegex is not a terminal handler, a request its pattern does not match is forwarded to the backend, and because the redirect pattern only accepts a numeric port while Traefik's host matcher canonicalizes the authority via net.SplitHostPort, a request with a non-numeric or empty port (for example 'Host: www.example.com:x') selects the sibling router, misses the redirect, and is proxied to the protected backend with none of the Ingress's annotation-derived middlewares applied. This discards not only authentication (e.g. BasicAuth) but every annotation-derived middleware, including source-IP allowlisting. Traefik v2 and v3 releases before v3.7.0 are not affected. The issue is fixed in v3.7.12.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
通过用户控制密钥绕过授权机制
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
traefik traefik 3.7.0 ~ 3.7.13 -

II. Public POCs for CVE-2026-88877

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III. Intelligence Information for CVE-2026-88877

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Vendor Advisories for CVE-2026-88877 (2)

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

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-2026-88011 5.3 MEDIUM Traefik: ForwardAuth identity spoofing via dot-form header alias
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-639

V. Comments for CVE-2026-88877

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