High Denial of service

CVE-2026-110354 — Infinite Loop in Haproxy

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.

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 0.8% (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

0.76%

ahead of 55% of scored CVEs · Oct 23, 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 Technologies 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 (denial of service), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Haproxy	Haproxy	≥ 3.0.0 and < 3.0.30≥ 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	≥ 3.0r1 and < 3.0r1-362.1441≥ 3.2r1 and < 3.2r1-378.1259≥ 3.3r1 and < 3.3r1-377.1005	Vulnerable	CVE Program (cve.org) e CISA ADP
HAProxy Technologies	HAProxy Kubernetes Ingress Controller	≥ 3.2.0 and < 3.2.17	Vulnerable	CVE Program (cve.org) e CISA ADP
HAProxy Technologies	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-835 · Infinite Loop

Other CVEs with this weakness →

EPSS over time FIRST

Oct 22, 2026 → Oct 23, 2026 · 2 reading(s) · max 0.76%

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).
Track CPU/memory spikes and availability drops correlated with request patterns.

web/proxy/WAF logsnetwork IDS/IPSresource metrics

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 technologies/haproxy kubernetes ingress controller, haproxy
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

Denial of service
same class

CWE-835
other pages naming this weakness

Related CVEs (same products)

High CVE-2026-110353 Unchecked Return Value in Haproxy 2d
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-2026-110354 is "Infinite Loop 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 0.76% 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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