Critical [CVE-2026-88879] Identity spoofing via HTTP header alias
This critical-severity Red Hat Linux advisory covers CVE-2026-88879 affecting Red Hat OpenShift Dev Spaces.
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Summary
A flaw was found in Traefik, an HTTP reverse proxy and load balancer. Due to a discrepancy in how Traefik and certain backend applications process HTTP header names, a remote attacker can smuggle specially crafted headers.
This allows the attacker to bypass identity assertions made by Traefik, leading to identity spoofing and potentially gaining unauthorized access or elevated privileges within the backend application. A flaw was found in Traefik's header canonicalization logic, where header names are canonicalized only on dashes.
A remote authenticated client can supply dot-form header aliases (e.g., X.Auth. User alongside X-Auth-User) to bypass Traefik middleware assertions.
When proxied to backends that collapse non-alphanumeric characters into singular variables (e.g., CGI, WSGI, PHP, NGINX), the backend resolves the attacker-controlled header value over Traefik's asserted identity. This leads to privilege escalation or identity spoofing within the downstream application context.
Red Hat severity: Critical — CVSS 9.6 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N). Weakness: CWE-444.
Affected Red Hat products: Red Hat OpenShift Dev Spaces. Red Hat lists Red Hat OpenShift GitOps as not affected.
Red Hat does not currently list a fixing RHSA for this CVE.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
Mitigation checklist
- Upgrade to fixed Traefik versions (v2.11.56, v3.7.12, or later) and explicitly configure the entrypoint option aliasHeadersStrategy to 'delete' or 'reject'. Alternatively, configure downstream backend web servers or WSGI/CGI gateways to strip or reject headers containing non-canonical characters before processing.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
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