High Logic error

CVE-2026-110353 — Unchecked Return Value in Haproxy

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.

Published Oct 22, 2026 · Updated Oct 22, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: mitre

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.7% (30-day exploitation probability)+8
Technical severity (high)+6
Automatable exploitation (SSVC)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.68%

ahead of 52% of scored CVEs · Oct 22, 2026

Affects

Haproxy

Haproxy and 3 more

CVSS base

7.5

High · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

None

none · proof-of-concept · active

Automatable

Yes

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Haproxy Haproxy, Haproxy HAProxy Enterprise Edition, Haproxy Kubernetes Ingress Controller…).
The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes matching the vulnerability class (logic error), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Haproxy	Haproxy	≥ 3.2.0 and < 3.2.26≥ 3.3.0 and < 3.3.17≥ 3.4.0 and < 3.4.6≥ 3.5-dev and < 3.5-dev9	Vulnerable	CVE Program (cve.org) e CISA ADP
Haproxy	HAProxy Enterprise Edition	≥ 3.2.0r1 and < 3.2r1-378.1259≥ 3.3.0r1 and < 3.3r1-377.1005	Vulnerable	CVE Program (cve.org) e CISA ADP
Haproxy	Kubernetes Ingress Controller	≥ 3.2.0 and < 3.2.17	Vulnerable	CVE Program (cve.org) e CISA ADP
Haproxy	Kubernetes Ingress Controller Enterprise	≥ 3.2.0 and < 3.2.17-ee1≥ 3.0 and < 3.0.16-ee17≥ 1.11 and < 1.11.14-ee11	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
7.5	CVSS 3.1	High	3.9	3.6	cve@mitre.org via NIST National Vulnerability Database
7.5	CVSS 3.1	High	—	—	mitre via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (score shown at the top: cve@mitre.org)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-252 · Unchecked Return Value

Other CVEs with this weakness →

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).

web/proxy/WAF logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first.

2026
SSVC assessment updated
Oct 22, 2026 · CVE Program (cve.org) e CISA ADP
Source status changed · Received → Awaiting Analysis
Oct 22, 2026 · NIST National Vulnerability Database
Affected products added · haproxy/haproxy, haproxy/haproxy enterprise edition, haproxy/kubernetes ingress controller, haproxy/kubernetes ingress c
Oct 22, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 22, 2026
CVSS changed · 7.5
Oct 22, 2026 · NIST National Vulnerability Database
Source status changed · → Received
Oct 22, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 22, 2026 · Alertas do Telegram
CVE published
Oct 22, 2026 · mitre

Source activity

Repeated readings are counted rather than listed.

1× References added · Oct 22, 2026 – Oct 22, 2026
1× Official description updated · Oct 22, 2026 – Oct 22, 2026

References

1 on the record

git.haproxy.org/
vendor-advisory, NIST National Vulnerability Database

Elsewhere on this site

Haproxy
every CVE for this vendor

Logic error
same class

CWE-252
other pages naming this weakness

Related CVEs (same products)

High CVE-2026-110354 Infinite Loop in Haproxy 1d
High CVE-2026-90678 An issue was discovered in HAProxy 3.3.0 through 3.4.4 and in 3.5-dev1 through 3.5-dev5… Sep 13, 2026
Low CVE-2026-26080 Unchecked Return Value in Haproxy Jul 20, 2026
Medium CVE-2026-26081 HAProxy Community Edition 3.0 through 3.3 before 3.3.3 lacks a length check for the… Jul 20, 2026
Critical CVE-2026-55203 HAProxy - Integer Overflow in FCGI Demux Record Length Field Jun 18, 2026
High CVE-2026-55204 HAProxy - NULL Pointer Dereference in hpack_dht_insert Function Jun 18, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-110353 is "Unchecked Return Value in Haproxy", rated High. It affects Haproxy (Haproxy); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.5 describes technical severity. EPSS 0.68% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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