CVE-2026-88879 Traefik - Authentication Bypass

Traefik v1.x, v2.x through v2.11.55, and v3.0.0 through v3.7.11 contain a HTTP header smuggling vulnerability caused by inconsistent header canonicalization, letting remote attackers bypass middleware identity checks, exploit requires crafted headers with dot-form aliases.

CVSS base score 8.2 /10
High
CISA KEV
Not listed
Public exploit
None known
Authentication
Not required
EPSS
0.29% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Authentication Bypass
Impact
Broken Authentication
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N
Published
10 September 2026
Updated
15 October 2026
Weakness
CWE-290

Vendor fix

Update to v2.11.56 or v3.7.12 and configure aliasHeadersStrategy to 'delete' or 'reject'.

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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