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CVE-2026-110354

HAProxy 3 before 3.4.6 allows a remote unauthenticated attacker to cause a denial of service (persistent worker-thread CPU exhaustion) via an HTTP/1.1 chunked request. Although the H1 multiplexer drai

HAProxy HAProxy
Open in ThreatlineRecord JSON
CVSS
7.5High
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.76%Chance of exploitation activity in the next 30 days, higher than 54% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in3.0.30Also 3.2.26, 3.3.17 and 9 moreCVE List
Published22 Oct 2026Updated 22 Oct 2026CVE List

What fixes it

Show all 12 fixed versions
  • 3.2r1-378.1259HAProxy Enterprise EditionCVE List
  • 3.3r1-377.1005HAProxy Enterprise EditionCVE List
  • 3.2.17HAProxy Kubernetes Ingress ControllerCVE List
  • 3.2.17-ee1Kubernetes Ingress Controller EnterpriseCVE List
  • 3.0.16-ee17Kubernetes Ingress Controller EnterpriseCVE List
  • 1.11.14-ee11Kubernetes Ingress Controller EnterpriseCVE List

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Description

HAProxy 3 before 3.4.6 allows a remote unauthenticated attacker to cause a denial of service (persistent worker-thread CPU exhaustion) via an HTTP/1.1 chunked request. Although the H1 multiplexer drains the request before closing the stream, the parser repeatedly re-processes the same bytes without making progress. The affected thread stays busy at 100% CPU after timeouts expire and after the client disconnects, and repeated requests can consume all worker threads until the process is restarted.

Text from CVE List

Affected versions 12

  • HAProxyaffected: 3.0.0 before 3.0.30CVE List
  • HAProxyaffected: 3.2.0 before 3.2.26CVE List
  • HAProxyaffected: 3.3.0 before 3.3.17CVE List
  • HAProxyaffected: 3.4.0 before 3.4.6CVE List
  • HAProxyaffected: 3.5-dev before 3.5-dev9CVE List
  • HAProxy Enterprise Editionaffected: 3.0r1 before 3.0r1-362.1441CVE List
  • HAProxy Enterprise Editionaffected: 3.2r1 before 3.2r1-378.1259CVE List
  • HAProxy Enterprise Editionaffected: 3.3r1 before 3.3r1-377.1005CVE List
  • HAProxy Kubernetes Ingress Controlleraffected: 3.2.0 before 3.2.17CVE List
  • Kubernetes Ingress Controller Enterpriseaffected: 3.2.0 before 3.2.17-ee1CVE List
  • Kubernetes Ingress Controller Enterpriseaffected: 3.0 before 3.0.16-ee17CVE List
  • Kubernetes Ingress Controller Enterpriseaffected: 1.11 before 1.11.14-ee11CVE List

References 1