CVE-2026-9256 — NGINX ngx_http_rewrite_module vulnerability

Description (CNA)

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 (CNA)

Vendor / product	Versions
F5 / NGINX Plus	affected 37.0 before 37.0.1.1; affected R36 before R36 P5; affected R32 before R32 P7
F5 / NGINX Open Source	affected 1.31.0 before 1.31.1; affected 1.30.0 before 1.30.2; affected 0.1.17 through 0.9.7

CWE

CWE-122

References

https://my.f5.com/manage/s/article/K000161377

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.

CVE

No English description supplied.

redhat-SADP

A flaw was found in the ngx_http_rewrite_module module of NGINX. When a rewrite directive uses a regex pattern with distinct, overlapping Perl-Compatible Regular Expression (PCRE) captures and a replacement string that references multiple such captures in a redirect or arguments context, an unauthenticated attacker can send crafted HTTP requests and cause a heap-based buffer overflow in the worker process, potentially allowing code execution or a denial of service by forcing the process to restart.