CVE-2026-42945

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module. This vulnerability exists when the rewrite directive is followed by a rewrite, if, or set directive and an unnamed Perl-Compatible Regular Expression (PCRE) capture (for example, $1, $2) with a replacement string that includes a question mark (?). An unauthenticated attacker along with conditions beyond its 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.  Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Affected products

Linuxmint, Nginx Open Source, Nginx Plus, Nginx, Red Os, Rocky Linux, Ubuntu

f5 Dos

≤ 4.7.0, 4.8.0

f5 Nginx Gateway Fabric

≤ 1.6.2, 2.5.1

f5 Nginx Ingress Controller

≤ 3.7.2, 4.0.1, 5.4.1

f5 Nginx Instance Manager

≤ 2.21.1

f5 Nginx Open Source

≤ 1.30.0

f5 Nginx Plus

≤ R36

Fix

Available

CVSS 4.0

9.2 CRITICAL

CVSS 3.1

8.1 HIGH

EPSS

66.0% (99th percentile)

Weakness

CWE-122, CWE-131

NVD status

Modified

Published

2026-05-13