CVE-2026-110353 HAProxy CVE debrief

Who should care

Defenders responsible for HAProxy and HAProxy Enterprise Edition deployments should assess exposure and potential impact. They should prioritize verifying exposure and assessing potential impact, focusing on HAProxy and HAProxy Enterprise Edition deployments, as a remote unauthenticated attacker can cause a denial of service (worker-thread CPU exhaustion) via a truncated HTTP/2 PING frame.

Why it matters

Defenders should prioritize verifying exposure and assessing potential impact, focusing on HAProxy and HAProxy Enterprise Edition deployments, as a remote unauthenticated attacker can cause a denial of service (worker-thread CPU exhaustion) via a truncated HTTP/2 PING frame.

• Denial of service (worker-thread CPU exhaustion)
• Potential for high CPU usage via sustained connections

Technical summary

The vulnerability exists in the h2c_handle_ping function in src/mux_h2.c, which does not check for a short read, unlike other H2 frame handlers. This oversight leads to CPU exhaustion as the incomplete frame cannot be processed, and its data is never consumed. The H2 multiplexer tasklet is repeatedly woken by that pending data without making progress, causing the CPU to spin until timeout or http-request closes the connection. An attacker opening many such connections can sustain high CPU usage. Defenders should prioritize verifying exposure and assessing potential impact, focusing on HAProxy and HAProxy Enterprise Edition deployments.

Defensive priority

Defenders should prioritize verifying exposure and assessing potential impact, focusing on HAProxy and HAProxy Enterprise Edition deployments.

Recommended defensive actions

• Verify HAProxy and HAProxy Enterprise Edition versions to determine exposure
• Assess potential impact on worker-thread CPU exhaustion
• Consider upgrading to version 3.4.6 or later
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and source item provide details on the vulnerability, including its description, affected versions, and potential impact. The CVE record was published on 2026-10-22T02:53:33.198Z and has not been modified since then. The source item provides additional context on the vulnerability. Defenders should verify exposure and assess potential impact, focusing on HAProxy and HAProxy Enterprise Edition deployments.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.