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Fencer Vulns
high 8.3

CVE-2026-32305 json

Traefik mTLS bypass via fragmented ClientHello SNI extraction failure

published 2026-03-20 7 mo ago modified 2026-07-15 3 mo ago also EUVD-2026-13663 , GHSA-wvvq-wgcr-9q48 , GO-2026-4793

cvss
8.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 36%
public exploits
0
none known

Summary

Traefik is an HTTP reverse proxy and load balancer. Versions 2.11.40 and below, 3.0.0-beta1 through 3.6.11, and 3.7.0-ea.1 are vulnerable to mTLS bypass through the TLS SNI pre-sniffing logic related to fragmented ClientHello packets. When a TLS ClientHello is fragmented across multiple records, Traefik's SNI extraction may fail with an EOF and return an empty SNI. The TCP router then falls back to the default TLS configuration, which does not require client certificates by default. This allows an attacker to bypass route-level mTLS enforcement and access services that should require mutual TLS authentication. This issue is patched in versions 2.11.41, 3.6.11 and 3.7.0-ea.2.

Patch / fix

  • go github.com/traefik/traefik/v3 3.6.11, 3.7.0-ea.2
  • go github.com/traefik/traefik/v2 2.11.41
  • Red Hat Red Hat OpenShift Dev Spaces 3.27 1776718585
  • Red Hat Red Hat OpenShift Dev Spaces 3.28 1779786779
  • govulncheck-vulndb openSUSE Leap 15.6 0.0.20260326T203309-150000.1.155.2

suse advisories SUSE-SU-2026:1135-1

  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1
  • traefik openSUSE Tumbleweed 3.6.12-1.1
  • traefik2 openSUSE Tumbleweed 2.11.42-1.1

opensuse advisories openSUSE-SU-2026:21483-1openSUSE-SU-2026:10444-1openSUSE-SU-2026:10445-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-32305 updated cvss 8.3

Traefik: github.com/traefik/traefik: Traefik: mTLS bypass allows unauthorized service access via fragmented ClientHello.

  • Red Hat OpenShift GitOps openshift-gitops-1/argo-rollouts-rhel8
    affected: workaround, no fix planned “Will not fix”
  • Red Hat OpenShift Dev Spaces 3.27 devspaces 1776718585
    fixed: vendor fix RHSA-2026:10175
  • Red Hat OpenShift Dev Spaces 3.28 devspaces/traefik-rhel9 1779786779
    fixed: vendor fix RHSA-2026:21772
  • Red Hat OpenShift Dev Spaces 3.27 devspaces 1776716842, devspaces 1776717247, devspaces 1776718438, devspaces 1776718450, devspaces 1776718480, devspaces 1776743204, +9 more Red Hat OpenShift Dev Spaces 3.28 devspaces/udi-rhel9 1779829736, devspaces/code-rhel9 1779814592, devspaces/server-rhel9 1779342423, devspaces/openvsx-rhel9 1779528224, devspaces/udi-base-rhel9 1779741066, devspaces/code-sshd-rhel9 1779813519, +9 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
7 mo ago

Exploit prediction

0.42% chance of exploitation in the next 30 days, higher than 36% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 7.8 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N
CISA ADP 3.1 8.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L
CNA 4.0 7.8 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
CNA 3.1 8.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L

Affected packages

ecosystem package affected fixed in
go github.com/traefik/traefik/v3
>=3.7.0-ea.1, <3.7.0-ea.2
<3.6.11
3.7.0-ea.2
3.6.11
go github.com/traefik/traefik/v2
<2.11.41
2.11.41
go github.com/traefik/traefik
<=1.7.34
all versions
 no fix listed

Affected products

  • traefik traefik
  • Red Hat Red Hat OpenShift Dev Spaces 3.27
  • Red Hat Red Hat OpenShift Dev Spaces 3.28
  • Red Hat Red Hat OpenShift GitOps

Classification

Weakness
  • CWE-287 Improper Authentication
  • CWE-1188 Initialization of a Resource with an Insecure Default
  • CWE-179 Incorrect Behavior Order: Early Validation

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.