CVE-2026-9256

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module. This vulnerability exists when a rewrite directive uses a regex pattern with distinct, overlapping Perl-Compatible Regular Expression (PCRE) captures (for example, ^/((.*))$) and a replacement string that references multiple such captures (for example, $1$2) in a redirect or arguments context. 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. 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 Nginx Open Source

≤ 0.9.7, 1.30.2, 1.31.0

f5 Nginx Plus

< R36, 37.0.0.1, R32

Fix

Available

CVSS 4.0

9.2 CRITICAL

CVSS 3.1

8.1 HIGH

EPSS

10.0% (95th percentile)

Weakness

CWE-122

NVD status

Modified

Published

2026-05-22