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Fencer Intel
medium 6.5

CVE-2025-66490 json

Traefik doesn't Prevent Path Normalization Bypass in Router + Middleware Rules

published 11mo ago modified 26d ago also EUVD-2025-201731 , GHSA-gm3x-23wp-hc2c , GO-2025-4206

cvss
6.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 40%
public exploits
0
none known

Summary

Traefik is an HTTP reverse proxy and load balancer. For versions prior to 2.11.32 and 2.11.31 through 3.6.2, requests using PathPrefix, Path or PathRegex matchers can bypass path normalization. When Traefik uses path-based routing, requests containing URL-encoded restricted characters (/, \, Null, ;, ?, #) can bypass the middleware chain and reach unintended backends. For example, a request to http://mydomain.example.com/admin%2F could reach service-a without triggering my-security-middleware, bypassing security controls for the /admin/ path. This issue is fixed in versions 2.11.32 and 3.6.3.

Patch / fix

  • go github.com/traefik/traefik/v2 2.11.32
  • go github.com/traefik/traefik/v3 3.6.3
  • traefik traefik 1.7.34, 2.11.32, 3.6.3
  • govulncheck-vulndb openSUSE Leap 15.6 0.0.20251230T014957-150000.1.134.1

suse advisories SUSE-SU-2026:0037-1

  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1
  • traefik2 openSUSE Tumbleweed 2.11.35-1.1
  • traefik openSUSE Tumbleweed 3.6.6-1.1

opensuse advisories openSUSE-SU-2026:21483-1openSUSE-SU-2026:10143-1openSUSE-SU-2026:10020-1

Is CVE-2025-66490 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

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-2025-66490 updated cvss 7.4

github.com/traefik/traefik: Traefik Path Normalization Bypass in Router + Middleware Rules

  • Red Hat OpenShift Dev Spaces (RHOSDS) 3.26 devspaces 1769638073
    fixed: vendor fix RHSA-2026:2456
  • Red Hat OpenShift Dev Spaces (RHOSDS) 3.26 devspaces 1769466457, devspaces 1769539518, devspaces 1769595755, devspaces 1769680738, devspaces 1769685154, devspaces 1769691754, +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
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
11mo ago

Exploit prediction

0.47% chance of exploitation in the next 30 days, higher than 40% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • github.com https://github.com/traefik/traefik/security/advisories/GHSA-gm3x-23wp-hc2c referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 6.9 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
CNA 4.0 6.9 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/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 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
go github.com/traefik/traefik
<=1.7.34
all versions
 no fix listed
go github.com/traefik/traefik/v2
<2.11.32
2.11.32
go github.com/traefik/traefik/v3
<3.6.3
3.6.3

Affected products

  • traefik traefik

Classification

Weakness

References

Sources

Fencer Intel 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.