Service crash via unbounded auth response buffering
Published Mar 5, 2026 · Updated Mar 5, 2026
Resource exhaustion in Traefik Proxy before 2.11.38 and before 3.6.9 allows remote authenticated users to crash it through ForwardAuth. The ForwardAuth response path in pkg/middlewares/auth/forward.go passes the authentication server body to io.ReadAll without a size limit, so a large or unbounded stream consumes process memory. Exploitation requires ForwardAuth and control over, or influence on, its authentication server response; one request can trigger an out-of-memory process kill and interrupt every route on the affected entrypoint.
Summary
What happened
Resource exhaustion in Traefik Proxy before 2.11.38 and before 3.6.9 allows remote authenticated users to crash it through ForwardAuth. The ForwardAuth response path in pkg/middlewares/auth/forward.go passes the authentication server body to io.ReadAll without a size limit, so a large or unbounded stream consumes process memory. Exploitation requires ForwardAuth and control over, or influence on, its authentication server response; one request can trigger an out-of-memory process kill and interrupt every route on the affected entrypoint.
The record
- CVE
- CVE-2026-26998
- Published
- Mar 5, 2026
- Updated
- Mar 5, 2026
- Vendor
- Traefik Labs
- Product
- Traefik Proxy
- Classifications
- CWE-770, T1499.004
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Mar 5, 2026CVE publishedPublication date reported by the CVE source.
- Mar 5, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 2.11.38
- Affected versionversion=< 3.6.9
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- ForwardAuth infinite-response proof of conceptfunctional · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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