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.

Metrics

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

Affected Vendors & Products

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Advisories

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Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://git.haproxy.org/?p=haproxy.git;a=commit;h=077906da140a35873bf451d7e9f67646c9f37c81 cve-icon cve-icon
History

Thu, 22 Oct 2026 06:00:00 +0000

Type Values Removed Values Added
Title Remote Denial of Service via HTTP Chunked Request in HAProxy

Thu, 22 Oct 2026 03:00:00 +0000

Type Values Removed Values Added
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.
Weaknesses CWE-835
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: mitre

Published:

Updated: 2026-10-22T02:46:38.255Z

Reserved: 2026-10-13T23:22:44.319Z

Link: CVE-2026-110354

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-22T03:16:31.427

Modified: 2026-10-22T03:16:31.427

Link: CVE-2026-110354

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-22T05:45:14Z

Weaknesses