CVE-2026-48491: Traefik is an HTTP reverse proxy and load balancer

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CRITICAL 10.0REMOTEUPGRADE

CVE-2026-48491 is a critical-severity flaw (CVSS 10.0) affecting traefik. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 HT

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	10.0 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 71%)
CISA exploited list	No
Weakness	CWE-288, CWE-807
Published	2026-06-23
Last modified	2026-09-02

Publisher (CNA): GitHub, Inc. · Vendor: traefik

Last updated 2026-09-02 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-23 20:16 UTCPublished CVE record published
2026-09-02 13:17 UTCUpdated Record last modified

traefik traefik UPGRADE

Affected: >= 3.7.0 and < 3.7.3

Fixed in: 3.7.3

Safe to downgrade to: a release before 3.7.0

1. Check installed version

apt-cache policy traefik || rpm -q traefik || traefik --version

2. UPGRADE to 3.7.3 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade traefik

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade traefik

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 3.7.0 (Debian / Ubuntu)

apt-cache madison traefik sudo apt install traefik=<VERSION_BEFORE_3.7.0> sudo apt-mark hold traefik

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list traefik sudo dnf downgrade traefik-<VERSION_BEFORE_3.7.0> sudo dnf versionlock add traefik

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-48491?

traefik: upgrade to 3.7.3. Exact commands for each OS are on this page.

Is CVE-2026-48491 being exploited?

CVE-2026-48491 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-48491 affect?

CVE-2026-48491 affects traefik. Severity is critical (CVSS 10.0). 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 throug

How urgent is CVE-2026-48491?

Priority 52/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

Traefik vulnerabilities

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References

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