CVE-2026-88008 Traefik - Authentication Bypass

Traefik 2.11.26 to 2.11.57 and 3.7.13 contain an authentication bypass caused by forwarding client-supplied Upgrade headers to backends supporting h2c, letting unauthenticated attackers access protected routes, exploit requires backend accepting h2c and returning 101 Switching Protocols.

CVSS base score 9.1 /10
Critical
CISA KEV
Not listed
Public exploit
Proof of concept available
EPSS
0.49% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Authentication Bypass
Impact
Broken Access Control
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Published
10 September 2026
Updated
15 October 2026
Weakness
CWE-444

Vendor fix

Upgrade to versions 2.11.57 or 3.7.13 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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