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VulnerabilityPublished

CVE-2026-110353: HAProxy · Unchecked Return Value

Affects HAProxySource CVE Database V5

0

Not known to be exploited · CVSS 7.5 High · fixed in 3.5-dev9 : patch HAProxy soon.

Data as of 26 Oct 2026, 12:42 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.7% chance of exploitation in 30 days – higher than 54% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers can reliably automate steps 1–4 of the kill chain
Technical impact
Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-10-22.

Patch
Available – fixed in 3.5-dev9, 3.4.6, 3.3.17 +7
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 22 Oct 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
HAProxyHAProxyAffected
  • >=3.5-dev <3.5-dev9
Fixed in
  • 3.5-dev9
HAProxyHAProxyAffected
  • >=3.4.0 <3.4.6
Fixed in
  • 3.4.6
HAProxyHAProxyAffected
  • >=3.3.0 <3.3.17
Fixed in
  • 3.3.17
HAProxyHAProxyAffected
  • >=3.2.0 <3.2.26
Fixed in
  • 3.2.26
HAProxyHAProxy Enterprise EditionAffected
  • >=3.3.0r1 <3.3r1-377.1005
Fixed in
  • 3.3r1-377.1005
HAProxyHAProxy Enterprise EditionAffected
  • >=3.2.0r1 <3.2r1-378.1259
Fixed in
  • 3.2r1-378.1259

Description

HAProxy 3.2 before 3.4.6 allows a remote unauthenticated attacker to cause a denial of service (worker-thread CPU exhaustion) via a truncated HTTP/2 PING frame. h2c_handle_ping in src/mux_h2.c does not check for a short read, unlike the other H2 frame handlers. Because the incomplete frame cannot be processed, its data is never consumed, and the H2 multiplexer tasklet is repeatedly woken by that pending data without making progress. The CPU spins until timeout http-request closes the connection, and an attacker opening many such connections can sustain high CPU usage.

References

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