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TI-2026-21476 Aliases CVE-2026-26998GHSA-fw45-f5q2-2p4x

Traefik: unbounded io.ReadAll on auth server response body causes OOM denial of service(DOS)

Priority LOW 21CWE-770Published · Updated

Key facts

Attack vector
Network
Privileges required
High
User interaction
None
Attack complexity
High
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Partial Red Hat: 1 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-770.

Summary

Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.38 and 3.6.9, there is a potential vulnerability in Traefik managing the ForwardAuth middleware responses. When Traefik is configured to use the ForwardAuth middleware, the response body from the authentication server is read entirely into memory without any size limit. There is no maxResponseBodySize configuration to restrict the amount of data read from the authentication server response. If the authentication server returns an unexpectedly large or unbounded response body, Traefik will allocate unlimited memory, potentially causing an out-of-memory (OOM) condition that crashes the process. This results in a denial of service for all routes served by the affected Traefik instance. This issue has been patched in versions 2.11.38 and 3.6.9.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00508 43rd percentileScored 2026-11-07
Fix Partial traefik (traefik): 2.11.38, 3.6.9github.com/traefik/traefik/v2 (Go): 2.11.38+1 more productRed Hat: 1 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
traefiktraefikbefore 2.11.38; before 3.6.92.11.38, 3.6.9Patch availableCNA
—github.com/traefik/traefik/v2 (Go)before 2.11.382.11.38Patch availableGHSA-fw45-f5q2-2p4x
—github.com/traefik/traefik/v3 (Go)before 3.6.93.6.9Patch availableGHSA-fw45-f5q2-2p4x
  • traefik Vendortraefik Affected before 2.11.38; before 3.6.9 Fixed in 2.11.38, 3.6.9 Patch available CNA
  • github.com/traefik/traefik/v2 (Go) Vendor— Affected before 2.11.38 Fixed in 2.11.38 Patch available GHSA-fw45-f5q2-2p4x
  • github.com/traefik/traefik/v3 (Go) Vendor— Affected before 3.6.9 Fixed in 3.6.9 Patch available GHSA-fw45-f5q2-2p4x

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*before 2.11.38; 3.0.0 to before 3.6.9Vulnerabletraefik
  • cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:* Versions before 2.11.38; 3.0.0 to before 3.6.9 Vulnerable ·traefik

Remediation

  • Fix · CNA traefik (traefik) Fixed in 2.11.38, 3.6.9
  • Fix · GHSA-fw45-f5q2-2p4x github.com/traefik/traefik/v2 (Go) Fixed in 2.11.38 Advisory →
  • Fix · GHSA-fw45-f5q2-2p4x github.com/traefik/traefik/v3 (Go) Fixed in 3.6.9 Advisory →

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat OpenShift Dev SpacesAffectedNo fix yet: Fix deferred

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-26998
  2. 2026-10-03 Alias added: GHSA-fw45-f5q2-2p4x

References

Patch 1

Advisory 1

Other 3

  • TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
  • TI-2023-25774 Uncontrolled Resource Consumption in Traefik CVSS 3.1HIGH 7.5
  • TI-2025-40914 Traefik doesn't Prevent Path Normalization Bypass in Router + Middleware Rules CVSS 4.0MEDIUM 6.9
  • TI-2022-07529 Authorization header displayed in the debug logs CVSS 3.1MEDIUM 6.5
  • TI-2024-30459 HTTP client can remove the X-Forwarded headers in Traefik CVSS 3.1CRITICAL 9.8
  • TI-2026-60261 Traefik v3.7.0 Authentication Bypass via from-to-www-redirect CVSS 4.0CRITICAL 9.3
See all 83 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences