Linux Distros Unpatched Vulnerability : CVE-2026-42055

critical Nessus Plugin ID 321739

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Synopsis

The Linux/Unix host has one or more packages installed with a vulnerability that the vendor indicates will not be patched.

Description

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

- NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_proxy_v2_module and ngx_http_grpc_module modules. This vulnerability exists when the proxy_http_version to 2 or grpc_pass directives are used to proxy HTTP/2 traffic, the ignore_invalid_headers directive is set to off, and the large_client_header_buffers directive size is larger than 2 megabytes. A remote, unauthenticated attacker, along with conditions beyond their control, could send large headers while creating an upstream request.
This may cause a heap-based buffer overflow in the NGINX worker process leading to a restart.
Additionally, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated. (CVE-2026-42055)

Note that Nessus relies on the presence of the package as reported by the vendor.

Solution

There is no known solution at this time.

Plugin Details

Severity: Critical

ID: 321739

File Name: unpatched_CVE_2026_42055.nasl

Version: 1.9

Type: Local

Agent: unix

Family: Misc.

Published: 6/20/2026

Updated: 7/8/2026

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

Risk Information

VPR

Risk Factor: High

Score: 7.7

Percentile: 99.06

CVSS v2

Risk Factor: Medium

Base Score: 6.8

Temporal Score: 5.8

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

CVSS Score Source: CVE-2026-42055

CVSS v3

Risk Factor: High

Base Score: 8.1

Temporal Score: 7.4

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

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

CVSS v4

Risk Factor: Critical

Base Score: 9.2

Threat Score: 7.2

Threat Vector: CVSS:4.0/E:U

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

Vulnerability Information

CPE: cpe:/o:canonical:ubuntu_linux:20.04:-:lts, p-cpe:/a:centos:centos:nginx-mod-mail, p-cpe:/a:centos:centos:nginx-mod-http-image-filter, p-cpe:/a:redhat:enterprise_linux:nginx-mod-mail, p-cpe:/a:redhat:enterprise_linux:nginx, p-cpe:/a:centos:centos:nginx-mod-devel, p-cpe:/a:centos:centos:nginx-all-modules, p-cpe:/a:redhat:enterprise_linux:nginx-mod-http-perl, cpe:/o:canonical:ubuntu_linux:18.04:-:lts, p-cpe:/a:centos:centos:nginx-mod-stream, p-cpe:/a:redhat:enterprise_linux:nginx-mod-devel, cpe:/o:centos:centos:8, p-cpe:/a:centos:centos:nginx, p-cpe:/a:redhat:enterprise_linux:nginx-filesystem, p-cpe:/a:centos:centos:nginx-mod-http-perl, cpe:/o:redhat:enterprise_linux:8, cpe:/o:canonical:ubuntu_linux:14.04:-:lts, p-cpe:/a:centos:centos:nginx-mod-http-xslt-filter, p-cpe:/a:centos:centos:nginx-filesystem, p-cpe:/a:redhat:enterprise_linux:nginx-all-modules, p-cpe:/a:redhat:enterprise_linux:nginx-mod-http-image-filter, p-cpe:/a:redhat:enterprise_linux:nginx-mod-stream, cpe:/o:canonical:ubuntu_linux:16.04:-:lts, p-cpe:/a:canonical:ubuntu_linux:nginx, p-cpe:/a:redhat:enterprise_linux:nginx-mod-http-xslt-filter

Required KB Items: Host/cpu, Host/local_checks_enabled, global_settings/vendor_unpatched, Host/OS/identifier

Exploit Ease: No known exploits are available

Vulnerability Publication Date: 6/17/2026

Reference Information

CVE: CVE-2026-42055

Detections

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