CVE-2026-26998 | Traefik: unbounded io.ReadAll on auth server response body causes OOM denial of service(DOS)

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.

Published: 2026-03-05 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-26998 is rated Low Risk (30.5/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.45%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-26998

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.02% 0.45% +0.43%
2 2026-03-06 — 0.02% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-26998

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
4.4 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:H)
They need powerful rights—admin, root, or similar—before this pays off.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 0.7 3.6 [email protected]

Weakness enumeration for CVE-2026-26998

GitHub Security Advisory for CVE-2026-26998

GHSA-fw45-f5q2-2p4x · Severity: medium · Ecosystem: go — Traefik has unbounded io.ReadAll on auth server response body that causes OOM DOS

OS Trackers for CVE-2026-26998

vendor priority summary link
alpine — CVE-2026-26998: 1 source package rows (traefik); 31 state rows across 2 repos (3.23-community, edge-community); fixed 0, open 31. https://security.alpinelinux.org/vuln/CVE-2026-26998
redhat medium — https://access.redhat.com/security/cve/CVE-2026-26998

Affected software / configurations for CVE-2026-26998

Vendor Product Version Raw CPE
traefik traefik < 2.11.38 cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*
traefik traefik >= 3.0.0, < 3.6.9 cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*

References for CVE-2026-26998

cvelogic Threat Intelligence