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AlmaLinux 9 : haproxy (ALSA-2026:55772)

critical Nessus Plugin ID 337658

Synopsis

The remote AlmaLinux host is missing one or more security updates.

Description

The remote AlmaLinux 9 host has a package installed that is affected by multiple vulnerabilities as referenced in the ALSA-2026:55772 advisory.

 * haproxy: HAProxy: Denial of Service via HPACK dynamic table insertions (CVE-2026-55204)
 * haproxy: HAProxy: Response smuggling due to integer overflow in FastCGI record length handling (CVE-2026-55203)

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

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

Solution

Update the affected haproxy package.

See Also

https://access.redhat.com/errata/RHSA-2026:55772

https://errata.almalinux.org/9/ALSA-2026-55772.html

Plugin Details

Severity: Critical

ID: 337658

File Name: alma_linux_ALSA-2026-55772.nasl

Version: 1.1

Type: Local

Published: 8/18/2026

Updated: 8/18/2026

Supported Sensors: Nessus Agent, Continuous Assessment, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.3

Percentile: 53.7

CVSS v2

Risk Factor: High

Base Score: 9.4

Temporal Score: 7

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

CVSS Score Source: CVE-2026-55203

CVSS v3

Risk Factor: Critical

Base Score: 9.1

Temporal Score: 7.9

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

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

CVSS v4

Risk Factor: Critical

Base Score: 9

Threat Score: 6.5

Threat Vector: CVSS:4.0/E:U

Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:L/SI:H/SA:N

Vulnerability Information

CPE: cpe:/o:alma:linux:9, cpe:/o:alma:linux:9::appstream, cpe:/o:alma:linux:9::baseos, cpe:/o:alma:linux:9::crb, cpe:/o:alma:linux:9::highavailability, cpe:/o:alma:linux:9::nfv, cpe:/o:alma:linux:9::realtime, cpe:/o:alma:linux:9::resilientstorage, cpe:/o:alma:linux:9::sap, cpe:/o:alma:linux:9::sap_hana, cpe:/o:alma:linux:9::supplementary, p-cpe:/a:alma:linux:haproxy

Required KB Items: Host/local_checks_enabled, Host/cpu, Host/AlmaLinux/release, Host/AlmaLinux/rpm-list

Exploit Ease: No known exploits are available

Patch Publication Date: 8/17/2026

Vulnerability Publication Date: 6/18/2026

Reference Information

CVE: CVE-2026-55203, CVE-2026-55204

CWE: 190, 476

RHSA: 2026:55772