CVE-2026-71324: Critical severity (CVSS 9.1)

Description

Traefik is an open source HTTP reverse proxy and load balancer. Prior to 2.11.53, 3.6.24, and 3.7.9, Traefik's default HTTP reverse proxy forwards a plain HTTP/2 or HTTP/3 CONNECT request and its body to an HTTP/1.1 upstream through a shared net/http.Transport. When the upstream answers the CONNECT with a keep-alive non-2xx response and does not drain the body, Traefik returns the desynchronized backend socket to its shared pool and reuses it for other clients. An unauthenticated attacker can use this behavior to make a different client read the attacker's smuggled response, which can include authenticated or private content from another request. The ForwardAuth middleware with forwardBody true and preserveRequestMethod true can re-issue a CONNECT with the buffered body attached, exposing the auth-client pool to the same desynchronization. This issue is fixed in 2.11.53, 3.6.24, and 3.7.9.

CVSS 3.1 breakdown

Attack vectorNetwork

Attack complexityLow

Privileges requiredNone

User interactionNone

ScopeUnchanged

ConfidentialityHigh

IntegrityHigh

AvailabilityNone

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

Affected products

Traefik Traefik≥ 3.0.0 < 3.6.24 · ≥ 3.7.0 < 3.7.9 · < 2.11.53

Remediation

Fixed in

Traefik Traefik≥ 3.6.24

Patch & vendor advisories

References

https://github.com/traefik/traefik/commit/04d36f28e4eae7535e96a6351dd9f7bfb48a30e7Patch
https://github.com/traefik/traefik/commit/0807b6d5dd1da8b2f7f4076ea2392b5437bf2ab0Patch
https://github.com/traefik/traefik/commit/94a7508817d180f0ab2f1eae93df48d4ab19eccePatch
https://github.com/traefik/traefik/pull/13542Issue TrackingPatch
https://github.com/traefik/traefik/pull/13543Issue TrackingPatch
https://github.com/traefik/traefik/pull/13556Issue TrackingPatch
https://github.com/traefik/traefik/releases/tag/v2.11.53Release Notes
https://github.com/traefik/traefik/releases/tag/v3.6.24Release Notes
https://github.com/traefik/traefik/releases/tag/v3.7.9Release Notes
https://github.com/traefik/traefik/security/advisories/GHSA-3ccp-42pg-hgv6PatchVendor Advisory

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

Frequently asked

Is CVE-2026-71324 being actively exploited?

CVE-2026-71324 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.55%.

How severe is CVE-2026-71324?

CVE-2026-71324 has a CVSS 3.1 base score of 9.1, rated critical. EPSS estimates a 0.55% probability of exploitation.

Which products are affected by CVE-2026-71324?

Affected products include Traefik Traefik.

How do I fix CVE-2026-71324?

Upgrade affected software to a fixed version, for example Traefik Traefik 3.6.24 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-71324 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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