CVE-2026-48491Traefik is an HTTP reverse proxy and load balancer.
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Traefik is an HTTP reverse proxy and load balancer. From 3.7.0 until 3.7.3, there is a high severity vulnerability in Traefik's domain-fronting protection (SNICheck) that allows an unauthenticated client to bypass mutual TLS enforced through wildcard router TLSOptions. When a router uses a wildcard host rule such as Host(*.example.com) with stricter TLS options (for example RequireAndVerifyClientCert), SNICheck resolves the TLS options for the HTTP Host header using exact map lookups only and never applies wildcard matching. If another permissive SNI is served on the same entrypoint, an attacker can complete the TLS handshake under the permissive options and then send an HTTP Host header targeting the wildcard-protected backend, reaching it without presenting a client certificate. This affects the regular HTTPS / HTTP-2 path and does not require HTTP/3. This vulnerability is fixed in 3.7.3.
- CVSS
- 10.0 CRITICAL (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N
- Weakness (CWE)
- CWE-288, CWE-807
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Modified
- Record last updated
- Sep 2, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
traefik traefik traefik:traefik | from 3.7.0 before 3.7.3 | NVD |
References
- https://github.com/traefik/traefik/releases/tag/v3.7.3patch, release-notes
- https://github.com/traefik/traefik/security/advisories/GHSA-5r4w-85f3-pw66exploit, mailing-list, patch, vendor-advisory
- https://access.redhat.com/errata/RHSA-2026:62260
- https://access.redhat.com/security/cve/CVE-2026-48491
- https://bugzilla.redhat.com/show_bug.cgi?id=2491923
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-48491.json
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.