CVE-2026-26080Network attack vector

Service interruption via unchecked QUIC varint

Published Jul 20, 2026 · Updated Jul 20, 2026

Denial of service in HAProxy 3.2 before 3.2.12 and 3.3 before 3.3.3 allows remote attackers to stop the process via a QUIC packet. The qc_parse_frm function in src/quic_frame.c ignores failure from quic_dec_int, leaving a malformed frame type as PADDING and misparsing the remaining packet. QUIC must be enabled; a truncated varint drives an infinite loop until the watchdog terminates the process, and repeated packets sustain the interruption.

CVSS severity3.7
Low
EPSS probability0.55%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in HAProxy 3.2 before 3.2.12 and 3.3 before 3.3.3 allows remote attackers to stop the process via a QUIC packet. The qc_parse_frm function in src/quic_frame.c ignores failure from quic_dec_int, leaving a malformed frame type as PADDING and misparsing the remaining packet. QUIC must be enabled; a truncated varint drives an infinite loop until the watchdog terminates the process, and repeated packets sustain the interruption.

The record

CVE
CVE-2026-26080
Published
Jul 20, 2026
Updated
Jul 20, 2026
Vendor
HAProxy Technologies
Product
HAProxy
Classifications
CWE-835, CWE-252, 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

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Is a vulnerable build present?

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

  1. Affected versionversion=3.2 <3.2.12
  2. Affected versionversion=3.3 <3.3.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

HAProxy Technologies · HAProxyversion=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
7.5Amazon LinuxCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.7MITRECVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
5.9Red HatCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
CWE-252Unchecked Return Value
T1499.004Endpoint Denial of Service: Application 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

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Your stack

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