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

Summary

CVE	CVE-2026-26999
State	PUBLISHED
Assigner	GitHub_M
Source Priority	CVE Program / NVD first with legacy fallback
Published	2026-03-05 19:16:05 UTC
Updated	2026-06-30 03:17:52 UTC
Description	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.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Problem Types: CWE-400 | CWE-772 | CWE-400 CWE-400: Uncontrolled Resource Consumption | CWE-772 Missing Release of Resource after Effective Lifetime

Version	Source	Type	Score	Severity	Vector
3.1	ADP	CVSS	7.5	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`
3.1	[email protected]	Secondary	7.5	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`
3.1	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	Secondary	7.5	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`
3.1	CNA	DECLARED	7.5	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`

CVSS v3.1 Breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

Type	Vendor	Product	Version	Update	Edition	Language
Application	Traefik	Traefik	All	All	All	All

Vendor Declared Affected Products

Source	Vendor	Product	Version	Platforms
CNA	Traefik	Traefik	affected < 2.11.38	Not specified
CNA	Traefik	Traefik	affected < 3.6.9	Not specified
ADP	Red Hat	Red Hat OpenShift Dev Spaces 3.27	Not specified	Not specified

References

Reference	Source	Link	Tags
github.com/traefik/traefik/releases/tag/v2.11.38	[email protected]	github.com	Product, Release Notes
bugzilla.redhat.com/show_bug.cgi	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	bugzilla.redhat.com
github.com/traefik/traefik/releases/tag/v3.6.9	[email protected]	github.com	Product, Release Notes
github.com/traefik/traefik/security/advisories/GHSA-xw98-5q62-jx94	[email protected]	github.com	Patch, Vendor Advisory
access.redhat.com/errata/RHSA-2026:10175	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	access.redhat.com
security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-26999.json	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	security.access.redhat.com
access.redhat.com/security/cve/CVE-2026-26999	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	access.redhat.com
CVE Program record	CVE.ORG	www.cve.org	canonical
NVD vulnerability detail	NVD	nvd.nist.gov	canonical, analysis

No vendor comments have been submitted for this CVE.

Additional Advisory Data

Source	Time	Event
ADP	2026-03-05T19:01:09.939Z	Reported to Red Hat.
ADP	2026-03-05T16:15:36.437Z	Made public.

Solutions

ADP: RHSA-2026:10175: Red Hat OpenShift Dev Spaces 3.27

Workarounds

ADP: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

There are currently no legacy QID mappings associated with this CVE.