8.8

CVE-2026-33433: Traefik Vulnerable to BasicAuth/DigestAuth Identity Spoofing via Non-Canonical headerField

Modified
AliasesGHSA-qr99-7898-vr7cGO-2026-4893CGA-225f-hmfg-4w33
Published 27-03-2026Last modified 15-07-2026

Vulnerability summary

CVE-2026-33433 is a high (CVSS 8.8) Authentication Bypass by Spoofing vulnerability in traefik. EPSS estimates a 0.49% chance of exploitation in the next 30 days, higher than 41.9% of scored vulnerabilities. 1 public exploit is recorded.

Priority
Routine

Not severe (CVSS 5.1, network access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
8.8/10
010
High · v3.1 (NVD)
EPSS score
0.49%
0%100%
Low · -0.08 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits1github

Advisory lineage

Upstream 0 · Downstream 2 · Related 3
OPENSUSE-SU-2026:21483-1SUSE-SU-2026:1205-1CGA-3GJM-565P-WGQH

Timeline

  1. 27-03-2026
    PublishedVulnerability first disclosed.
  2. 15-07-2026
    Last modifiedVulnerability information updated.

Description

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.

CVSS metrics

6 scores · 4 sources · 2 versions

EPSS trend

Probability

0.49%

Chance of exploitation in the next 30 days

Percentile

42%

Versus all other CVEs

30-day change

Decrease -0.08 pp

From 0.56% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

1 found
  • githubUnverified

    Traefik

    Maturity: poc

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, administrative account, no user interaction (CVSS vector). Other conditions: not stated in public data.

Chainguard4 products
  • traefik-2.11< 2.11.42-r0
  • traefik-3.5All versions (No fix recorded)
  • traefik-fips-2.11< 2.11.42-r0
  • traefik-fips-3.5All versions (No fix recorded)
Github.com/traefik/traefik2 products
  • v2< 2.11.42
  • v3≥ 3.0.0-beta1, < 3.6.12 | ≥ 3.7.0-ea.1, < 3.7.0-ea.3
Github.com/traefik1 product
  • traefikAll versions (No fix recorded)
Traefik1 product
  • traefik≥ 3.0.0-beta1, < 3.6.11 | ≥ 3.7.0-ea.1, < 3.7.0-ea.3 | < 2.11.42 | ≥ 3.0.0, < 3.6.12 | 3.7.0:ea1 | 3.7.0:ea2

4 vendors · 8 products

References

11 links
Show all 11 references