CVE detail
CVE-2026-39858
Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.43, 3.6.14, and 3.7.0-rc.2, there is a high severity authentication bypass vulnerability in Traefik's ForwardAuth and snippet-based authentication middleware. Traefik's forwarded-header sanitization logic targets only canonical header names (e.g., X-Forwarded-Proto) and does not strip or normalize alias variants that use underscores instead of dashes (e.g., X_Forwarded_Proto). These unsanitized alias headers are forwarded intact to the authentication backend. When the backend normalizes underscore and dash header forms equivalently, an attacker can inject spoofed trust context — such as a trusted scheme or host — through the alias headers and bypass authentication on protected routes without valid credentials. This issue has been patched in versions 2.11.43, 3.6.14, and 3.7.0-rc.2.
Buzz score
Why this CVE is surfacing
This all-time snapshot uses the same composite formula as Trending across a 30-year evidence window, rather than a current rolling window.
Buzz score components · mention 22.0 · diversity 13.0 · KEV 0.0 · OTX 0.0 · PoC 0.0
Why it matters now
Mention timeline
- Total mentions
- 0
- within the 30d window
- Peak daily
- 0
- highest bucket
Evidence
Source links by recency
8 source links · newest first
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-39858.jsonsecurity.access.redhat.com
No excerpt available.
Vendor Advisorysecurity.access.redhat.comApr 30, 2026, 9:16 PM - https://bugzilla.redhat.com/show_bug.cgi?id=2464234bugzilla.redhat.com
No excerpt available.
Exploitbugzilla.redhat.comApr 30, 2026, 9:16 PM - https://access.redhat.com/security/cve/CVE-2026-39858access.redhat.com
No excerpt available.
Vendor Advisoryaccess.redhat.comApr 30, 2026, 9:16 PM - https://access.redhat.com/errata/RHSA-2026:21772access.redhat.com
No excerpt available.
Vendor Advisoryaccess.redhat.comApr 30, 2026, 9:16 PM No excerpt available.
Exploitgithub.comApr 30, 2026, 9:16 PMNo excerpt available.
Exploitgithub.comApr 30, 2026, 9:16 PMNo excerpt available.
Exploitgithub.comApr 30, 2026, 9:16 PMNo excerpt available.
Exploitgithub.comApr 30, 2026, 9:16 PM
Exploit code
Public exploit repository references
Public PoC repositories are third-party, potentially unsafe artifacts. Treat their code as untrusted and use it only on authorized systems in an isolated, least-privilege environment. cvebuzz does not execute the code or verify that an exploit works.
0 repository references · best confidence N/A · max 0 stars
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