CVE-2026-26081Network attack vector

Unauthenticated process crash via QUIC token underflow

Published Jul 20, 2026 · Updated Jul 20, 2026

Denial of service in HAProxy Community 3.0 through 3.3 allows remote attackers to crash the process with a malformed QUIC Initial packet. The QUIC token parser accepts a NEW_TOKEN value whose length differs from QUIC_TOKEN_LEN, allowing token-validation arithmetic to underflow. Unauthenticated network access to a QUIC-enabled listener is required, and repeated packets can keep the proxy service unavailable.

CVSS severity7.5
High
EPSS probability0.48%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Denial of service in HAProxy Community 3.0 through 3.3 allows remote attackers to crash the process with a malformed QUIC Initial packet. The QUIC token parser accepts a NEW_TOKEN value whose length differs from QUIC_TOKEN_LEN, allowing token-validation arithmetic to underflow. Unauthenticated network access to a QUIC-enabled listener is required, and repeated packets can keep the proxy service unavailable.

The record

CVE
CVE-2026-26081
Published
Jul 20, 2026
Updated
Jul 20, 2026
Vendor
HAProxy Technologies
Product
HAProxy
Classifications
CWE-130, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 20, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 20, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.0 <3.0.12
  2. Affected versionversion=3.1 <3.1.14
  3. Affected versionversion=3.2 <3.2.12
  4. Affected versionversion=3.3 <3.3.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

HAProxy Technologies · HAProxyversion=3.0 <3.0.12; version=3.1 <3.1.14; version=3.2 <3.2.12; version=3.3 <3.3.3

Published CVSS scores

7.5HAProxy TechnologiesCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
4.8MITRECVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-130Improper Handling of Length Parameter Inconsistency
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo