CVE-2026-88011
HIGHDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 15% of all known CVEs.
References
Related Vulnerabilities
Other CWE-290 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2024-4358 | Critical | 9.8 | 97% | KEV | - |
| CVE-2022-24112 | Critical | 9.8 | 96% | KEV | Fix |
| CVE-2022-23131 | Critical | 9.1 | 96% | KEV | - |
| CVE-2021-29441 | High | 8.6 | 88% | - | Fix |
| CVE-2019-1234 | High | 7.5 | 75% | - | - |
| CVE-2021-31195 | Medium | 6.5 | 74% | - | Fix |
Common questions
How do I fix CVE-2026-88011?
Upgrade traefik to 2.11.56 or later.
Is CVE-2026-88011 being actively exploited?
Not that we know of. CVE-2026-88011 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.24% is the estimated probability that it will be exploited in the next 30 days. That is higher than 15% of all scored CVEs.
How severe is CVE-2026-88011?
CVE-2026-88011 has a CVSS v3 base score of 8.1, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-88011 affect?
Published advisories record a fix for traefik (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-09-15.