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TI-2026-21477 Aliases CVE-2026-26999GHSA-xw98-5q62-jx94

Traefik: tcp router clears read deadlines before tls forwarding, enabling stalled handshakes (slowloris doS)

Priority MEDIUM 40CWE-400Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-400.

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 TLS handshake on TCP routers. When Traefik processes a TLS connection on a TCP router, the read deadline used to bound protocol sniffing is cleared before the TLS handshake is completed. When a TLS handshake read error occurs, the code attempts a second handshake with different connection parameters, silently ignoring the initial error. A remote unauthenticated client can exploit this by sending an incomplete TLS record and stopping further data transmission, causing the TLS handshake to stall indefinitely and holding connections open. By opening many such stalled connections in parallel, an attacker can exhaust file descriptors and goroutines, degrading availability of all services on the affected entrypoint. 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 0.00612 49th percentileScored 2026-11-07
Fix Fixed traefik (traefik): 2.11.38, 3.6.9github.com/traefik/traefik/v2 (Go): 2.11.38+1 more productRed Hat: 1 advisory

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
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-xw98-5q62-jx94
—github.com/traefik/traefik/v3 (Go)before 3.6.93.6.9Patch availableGHSA-xw98-5q62-jx94
  • 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-xw98-5q62-jx94
  • github.com/traefik/traefik/v3 (Go) Vendor— Affected before 3.6.9 Fixed in 3.6.9 Patch available GHSA-xw98-5q62-jx94

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-xw98-5q62-jx94 github.com/traefik/traefik/v2 (Go) Fixed in 2.11.38 Advisory →
  • Fix · GHSA-xw98-5q62-jx94 github.com/traefik/traefik/v3 (Go) Fixed in 3.6.9 Advisory →

Red Hat 1 advisory

  • RHSA-2026:10175 Released 2026-04-23 · Red Hat rating Important
    Red Hat OpenShift Dev Spaces 3.27.1 Release.
    • Red Hat OpenShift Dev Spaces 3.27 registry.redhat.io/devspaces/code-rhel9, registry.redhat.io/devspaces/dashboard-rhel9, registry.redhat.io/devspaces/devspaces-rhel9-operator +8

Vendor assessments

Red Hat

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

ProductStatusPlan or fix
Red Hat OpenShift Dev Spaces 3.27Fixed RHSA-2026:10175
Not affected: 1 product
  • Red Hat OpenShift Dev Spaces 3.27

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-26999
  2. 2026-10-03 Alias added: GHSA-xw98-5q62-jx94
  3. 2026-10-25 EPSS moved to the below the 50th percentile

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