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Fencer Vulns
high 7.7

CVE-2026-33433 json

Traefik Vulnerable to BasicAuth/DigestAuth Identity Spoofing via Non-Canonical headerField

published 2026-03-27 7 mo ago modified 2026-11-04 5 d ago also EUVD-2026-16616 , GHSA-qr99-7898-vr7c , GO-2026-4893

cvss
7.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 42%
public exploits
0
none known

Summary

Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.42, 3.6.11, and 3.7.0-ea.3, when `headerField` is configured with a non-canonical HTTP header name (e.g., `x-auth-user` instead of `X-Auth-User`), an authenticated attacker can inject their own canonical version of that header to impersonate any identity to the backend. The backend receives two header entries — the attacker-injected canonical one is read first, overriding Traefik's non-canonical write. Versions 2.11.42, 3.6.11, and 3.7.0-ea.3 patch the issue.

Patch / fix

  • go github.com/traefik/traefik/v2 2.11.42
  • go github.com/traefik/traefik/v3 3.6.12, 3.7.0-ea.3
  • Red Hat Red Hat OpenShift Dev Spaces 3.27 1776718585
  • govulncheck-vulndb openSUSE Leap 15.6 0.0.20260402T184258-150000.1.158.1

suse advisories SUSE-SU-2026:1205-1

  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1

opensuse advisories openSUSE-SU-2026:21483-1

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-2026-33433 updated cvss 7.7

github.com/traefik/traefik: Traefik: Authentication bypass via non-canonical HTTP header injection

  • Red Hat OpenShift Dev Spaces 3.27 devspaces 1776718585
    fixed: vendor fix RHSA-2026:10175
  • Red Hat OpenShift Dev Spaces 3.27 devspaces 1776716842, devspaces 1776717247, devspaces 1776718438, devspaces 1776718450, devspaces 1776718480, devspaces 1776743204, +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
no
Technical impact
partial
Assessed
7 mo ago

Exploit prediction

0.49% chance of exploitation in the next 30 days, higher than 42% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/traefik/traefik/security/advisories/GHSA-qr99-7898-vr7c referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 5.1 CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N
CISA ADP 3.1 7.7 CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:N
GitHub 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CNA 4.0 5.1 CVSS:4.0/AV:N/AC:H/AT:P/PR:H/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 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CNA 3.1 7.7 CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:N

Affected packages

ecosystem package affected fixed in
go github.com/traefik/traefik/v2
<2.11.42
2.11.42
go github.com/traefik/traefik/v3
>=3.0.0-beta1, <3.6.12
>=3.7.0-ea.1, <3.7.0-ea.3
3.6.12
3.7.0-ea.3
go github.com/traefik/traefik
all versions
 no fix listed

Affected products

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

Classification

Weakness
  • CWE-290 Authentication Bypass by Spoofing

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.