Debian dla-4842 : haproxy - security update

medium Nessus Plugin ID 366978

Synopsis

The remote Debian host is missing a security-related update.

Description

The remote Debian 12 host has packages installed that are affected by a vulnerability as referenced in the dla-4842 advisory.

------------------------------------------------------------------------- Debian LTS Advisory DLA-4842-1 [email protected] https://www.debian.org/lts/security/ Santiago Ruano Rincn October 18, 2026 https://wiki.debian.org/LTS
-------------------------------------------------------------------------

Package : haproxy Version : 2.6.12-1+deb12u4 CVE ID : CVE-2026-33555, not yet available

Three vulnerabilities were discovered in HAProxy, a fast and reliable load balancing reverse proxy, which could result in denial of service or HTTP request smuggling.

CVE-2026-33555

Martino Spagnuolo reported that the HTTP/3 parsing code in HAProxy, a fast and reliable load balancing reverse proxy, does not properly validate the received body size and the announced content-length header, which may result in HTTP request smuggling. It is to note that these features are not enabled by default in the binary packages distributed with Debian bookworm.

Two other vulnerabilities, that may result in denial of service, don't have a CVE assigned yet.

For Debian 12 bookworm, these problems have been fixed in version 2.6.12-1+deb12u4.

We recommend that you upgrade your haproxy packages.

For the detailed security status of haproxy please refer to its security tracker page at:
https://security-tracker.debian.org/tracker/haproxy

Further information about Debian LTS security advisories, how to apply these updates to your system and frequently asked questions can be found at: https://wiki.debian.org/LTS Attachment:
signature.asc Description: PGP signature

Tenable has extracted the preceding description block directly from the Debian security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Solution

Upgrade the haproxy packages.

Plugin Details

Severity: Medium

ID: 366978

File Name: debian_DLA-4842.nasl

Version: 1.1

Type: Local

Agent: unix

Family: Debian Local Security Checks

Published: 10/18/2026

Updated: 10/18/2026

Supported Sensors: Frictionless Assessment Agent, Nessus Agent, Agentless Assessment, Continuous Assessment, Tenable Cloud Security, Tenable Self-Hosted Container Security, Nessus

Risk Information

VPR

Risk Factor: Low

Score: 1.2

Percentile: 0.01

CVSS v2

Risk Factor: Medium

Base Score: 5

Temporal Score: 3.9

Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:P/A:N

CVSS Score Source: CVE-2026-33555

CVSS v3

Risk Factor: Medium

Base Score: 5.8

Temporal Score: 5.2

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N

Temporal Vector: CVSS:3.0/E:P/RL:O/RC:C

Vulnerability Information

CPE: cpe:/o:debian:debian_linux:12.0, p-cpe:/a:debian:debian_linux:haproxy-doc, p-cpe:/a:debian:debian_linux:haproxy, p-cpe:/a:debian:debian_linux:vim-haproxy

Required KB Items: Host/local_checks_enabled, Host/Debian/release, Host/Debian/dpkg-l

Exploit Available: true

Exploit Ease: Exploits are available

Patch Publication Date: 10/18/2026

Vulnerability Publication Date: 4/13/2026

Reference Information

CVE: CVE-2026-33555

IAVB: 2026-B-0103

Detections

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