RHEL 9 : haproxy (RHSA-2026:55802)

critical Nessus Plugin ID 336001

Synopsis

The remote Red Hat host is missing one or more security updates for haproxy.

Description

The remote Redhat Enterprise Linux 9 host has a package installed that is affected by multiple vulnerabilities as referenced in the RHSA-2026:55802 advisory.

The haproxy packages provide a reliable, high-performance network load balancer for TCP and HTTP-based applications.

Security Fix(es):

* 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)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Tenable has extracted the preceding description block directly from the Red Hat Enterprise Linux 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 RHEL haproxy package based on the guidance in RHSA-2026:55802.

Plugin Details

Severity: Critical

ID: 336001

File Name: redhat-RHSA-2026-55802.nasl

Version: 1.1

Type: Local

Agent: unix

Family: Red Hat Local Security Checks

Published: 8/17/2026

Updated: 8/17/2026

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

Risk Information

VPR

Risk Factor: Medium

Score: 4.3

Percentile: 53.7

Vendor

Vendor Severity: Important

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:redhat:rhel_e4s:9.2, p-cpe:/a:redhat:enterprise_linux:haproxy

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

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: 2026:55802

Detections

Analytics