Traefik is a widely used Kubernetes ingress/reverse-proxy; this auth-bypass can expose protected backends across many cloud-native deployments and disrupt enterprise apps.
CVE-2026-88877
Traefik v3.7.0–3.7.11 authentication bypass via host/port handling
Is CVE-2026-88877 being exploited?
Not confirmed. CVE-2026-88877 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.44% probability of exploitation in the next 30 days.
How severe is CVE-2026-88877?
CVE-2026-88877 is rated Critical with a CVSS score of 9.3. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-88877?
Yes. A fix has been recorded for CVE-2026-88877. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-88877 affect?
CVE-2026-88877 affects Traefik v3.7.0–3.7.11, Kubernetes ingress-nginx provider configurations using auth + from-to-www-redirect, Services behind Traefik ingress. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-88877?
Upgrade to Traefik v3.7.12 immediately; apply temporary Host header filtering if unable to patch.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Annotation-derived middleware (including auth and IP allowlists) can be bypassed, allowing unauthenticated requests proxied to protected backends.
Immediate action required
- affected>= 3.7.0 and <= 3.7.13
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.