Authentication bypass via redirect-only sibling router
Published Sep 10, 2026 · Updated Sep 10, 2026
Authentication bypass in Traefik Proxy 3.7.0 through 3.7.11 allows remote attackers to reach protected backends via a crafted Host header. applyFromToWwwRedirect creates a host-only sibling router that retains the backend service but replaces every annotation-derived middleware with a nonterminal RedirectRegex. An Ingress must combine an authentication or access-control annotation with from-to-www-redirect; a nonnumeric or empty port then falls through without those controls.
Summary
What happened
Authentication bypass in Traefik Proxy 3.7.0 through 3.7.11 allows remote attackers to reach protected backends via a crafted Host header. applyFromToWwwRedirect creates a host-only sibling router that retains the backend service but replaces every annotation-derived middleware with a nonterminal RedirectRegex. An Ingress must combine an authentication or access-control annotation with from-to-www-redirect; a nonnumeric or empty port then falls through without those controls.
The record
- CVE
- CVE-2026-88877
- Published
- Sep 10, 2026
- Updated
- Sep 10, 2026
- Vendor
- Traefik Labs
- Product
- Traefik Proxy
- Classifications
- T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 10, 2026CVE publishedPublication date reported by the CVE source.
- Sep 10, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=3.7.0 <=3.7.13
What conditions does exploitation require?
What is affected?
Published CVSS scores
No CVSS assessment is available in this record.
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Upstream-linked from-to-www-redirect reproduction bundlefunctional · demonstrated
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Technologies
Your stack
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Your stack
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