CVE-2026-88011

Medium

Elevated severity or exploit probability.

CVSS base

8.1 HIGH

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

EPSS — probability of exploitation (30 days)

0.2%

14.7th percentile

CISA KEV

Not listed

Weakness / dates

CWE-290

Published 2026-09-10 · modified 2026-09-15

CVSS breakdown

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Attack Vector	N	Network
Attack Complexity	L	Low
Privileges Required	L	Low
User Interaction	N	None
Scope	U	Unchanged
Confidentiality	H	High
Integrity	H	High
Availability	N	None

Timeline

2026-09-10 — Published (NVD)
2026-09-15 — Last modified (NVD)

Description

Traefik is an open source HTTP reverse proxy and load balancer. Prior to 2.11.56, and from 3.0.0 until 3.7.12, a client-supplied dot-form header such as X.Authenticated.User survives ForwardAuth replacement and underscoreHeadersStrategy because Go treats it as distinct from X-Authenticated-User while normalization-prone CGI, WSGI, PHP, and NGINX backends collapse both names. A backend can consequently consume the client value instead of the identity Traefik asserted, allowing identity spoofing for any header managed by Traefik. The aliasHeadersStrategy protection is disabled by default and must be configured as delete or reject. The mitigation is available in 2.11.56 and 3.7.12.

Affected

traefik

References

Official: NVD · CVE.org