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CVE-2026-48491

Traefik authentication bypass

10.0 CRITICALPublic exploitEPSS 0.36%
  1. Published23 Jun 2026

Description

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 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeChanged
ConfidentialityHigh
IntegrityHigh
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N

Affected products

Traefik≥ 3.7.0 < 3.7.3

Remediation

Fixed in
Traefik≥ 3.7.3

References

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Frequently asked

Is CVE-2026-48491 being actively exploited?

CVE-2026-48491 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.36%.

How severe is CVE-2026-48491?

CVE-2026-48491 has a CVSS 3.1 base score of 10.0, rated critical. EPSS estimates a 0.36% probability of exploitation.

Which products are affected by CVE-2026-48491?

Affected products include Traefik.

How do I fix CVE-2026-48491?

Upgrade affected software to a fixed version, for example Traefik 3.7.3 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-48491 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.