Detections
Analytics

nginx 0.9.x < 1.30.4 / 1.31.x < 1.31.3 Heap-based Buffer Overflow

critical Nessus Plugin ID 366466

Synopsis

The remote web server is affected by a heap-base buffer overflow vulnerability.

Description

According to its Sever response header, the installed version of nginx is 0.9.x prior to 1.30.4 or 1.31.x prior to 1.31.3. It is, therefore, affected by the following issue :

 - A vulnerability exists in NGINX Plus and NGINX Open Source when a map directive uses regex matching and a string expression references the map's regex capture variables before referencing the map output variable.
 Alternatively, the same result could be achieved by using a non-cacheable variable in a string expression under certain conditions. An unauthenticated attacker along with conditions beyond their control can exploit this vulnerability by sending crafted HTTP requests. This may cause a heap 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. Impact: This vulnerability may allow remote attackers to cause a denial-of-service (DoS) on the NGINX system or to possibly trigger a code execution. There is no control plane exposure; this is a data plane issue only.
 Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
 (CVE-2026-42533)

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

Solution

Upgrade to nginx 1.30.4 or 1.31.3 or later.

See Also

https://my.f5.com/manage/s/article/K000162097

https://nginx.org/en/security_advisories.html

https://www.cve.org/CVERecord?id=CVE-2026-42533

Plugin Details

Severity: Critical

ID: 366466

File Name: nginx-CVE-2026-42533.nasl

Version: 1.1

Type: Combined

Agent: unix

Family: Web Servers

Published: 10/16/2026

Updated: 10/16/2026

Configuration: Enable paranoid mode

Supported Sensors: Nessus Agent, Nessus

Risk Information

VPR

Risk Factor: High

Score: 7.9

Percentile: 99.35

CVSS v2

Risk Factor: High

Base Score: 7.6

Temporal Score: 6.3

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

CVSS Score Source: CVE-2026-42533

CVSS v3

Risk Factor: High

Base Score: 8.1

Temporal Score: 7.5

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:F/RL:O/RC:C

CVSS v4

Risk Factor: Critical

Base Score: 9.2

Threat Score: 8.2

Threat Vector: CVSS:4.0/E:P

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

Vulnerability Information

CPE: cpe:/a:nginx:nginx

Required KB Items: Settings/ParanoidReport, installed_sw/nginx

Exploit Available: true

Exploit Ease: Exploits are available

Vulnerability Publication Date: 7/15/2026

Reference Information

CVE: CVE-2026-42533

IAVA: 2026-A-0754