CVE-2026-85597: Traefik before v2.11.55 and v3.0.0 through v3.7.10 contain a TLS option conflict resolution vulnerability that

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CRITICAL 9.1REMOTEUPGRADE

CVE-2026-85597 is a critical-severity flaw (CVSS 9.1) affecting traefik. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Traefik before v2.11.55 and v3.0.0 through v3.7.10 contain a TLS option conflict resolution vulnerability that allows unauthenticated attackers to bypass client-certificate authentication by creating conflicting TLS options on multi-host routers. Attackers can reach protected backends by exploiting shared TLS resolution across multiple hostnames in a single router rule, causing the strict mTLS requirement to fall back to default options for all h

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	9.1 (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-863
Published	2026-09-04
Last modified	2026-10-08

Publisher (CNA): VulnCheck · Vendor: traefik

Last updated 2026-10-08 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-09-04 12:17 UTCPublished CVE record published
2026-10-08 16:17 UTCUpdated Record last modified

traefik traefik UPGRADE

Affected: < 2.11.55 · >= 3.0.0 and < 3.7.11

Fixed in: 2.11.55, 3.7.11

Safe to downgrade to: a release before 3.0.0

1. Check installed version

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

2. UPGRADE to 2.11.55 (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 3.0.0 (Debian / Ubuntu)

apt-cache madison traefik sudo apt install traefik=<VERSION_BEFORE_3.0.0> 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_3.0.0> 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-2026-85597?

traefik: upgrade to 2.11.55, 3.7.11. Exact commands for each OS are on this page.

Is CVE-2026-85597 being exploited?

CVE-2026-85597 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-2026-85597 affect?

CVE-2026-85597 affects traefik. Severity is critical (CVSS 9.1). Traefik before v2.11.55 and v3.0.0 through v3.7.10 contain a TLS option conflict resolution vulnerability that allows unauthenticated attackers to bypass client-certificate authentication by creating conflicting TLS options on multi-host ro

How urgent is CVE-2026-85597?

Priority 49/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

Traefik vulnerabilities

Related CVEs

CVE-2026-65600 MEDIUM 5.3 UPGRADE Traefik versions <= v2.11.51, >= v3.6.0 <= v3.6.22, and >= v3.7.0 <= v3.7.6 contain an authentication bypass v
CVE-2026-112778 HIGH 8.8 UPGRADE Traefik before 2.11.46, 3.x before 3.6.17, and 3.7.0 lack namespace validation for Ingress and Service annotat
CVE-2026-88879 HIGH 8.2 UPGRADE Traefik is an HTTP reverse proxy and load balancer
CVE-2026-88878 MEDIUM 5.3 UPGRADE Traefik is an HTTP reverse proxy and load balancer
CVE-2026-88877 CRITICAL 9.8 UPGRADE Traefik is a HTTP reverse proxy and load balancer

References

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