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.
Published October 25, 2026Updated October 26, 2026
Source data
Overview
Full source title
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.
The source does not supply a plain-text overview. Review the authoritative advisory for the full description.
Impact & technical details
A separate impact classification is not supplied in this record. See the source advisory.
- CVSS base score
- 7.5 / 10
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Highest base score supplied by MSRC for this record; the vector belongs to that score. Ratings can vary by product. Microsoft Important is displayed as High; Moderate is displayed as Medium.
Affected products
- azl3 haproxy 2.9.11-8 on Azure Linux 3.0
Source guidance
Remediation
- Release Notes
Patch availability is not confirmed by this dataset. Consult the vendor before selecting a remediation.
GTP recommendation · Rule-based guidance
Recommended next step
Review affected Microsoft products and apply the applicable security updates through your organization's normal patch-management process. Confirm availability and prerequisites in the Microsoft advisory.
Authoritative sources & updates
Findings and update information come from the linked publishers. GTP compiles the public record and provides the recommendation above. CVSS ratings shown here come from Microsoft. NVD references provide additional public context.
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Security bulletins are provided for informational purposes and compiled from authoritative public sources. Vulnerability applicability varies by environment. Validate affected products, configuration, compatibility requirements, and vendor guidance before making production changes.