NGINX: Malicious requests can cause a system crash or code execution

Summary

A security issue in NGINX's rewrite module can be exploited by sending specially crafted HTTP requests. This may cause the system to crash or allow an attacker to execute malicious code. If you're using NGINX, update to the latest version to ensure you have the fix.

What to do

Update nginx to version 1.28.3-r2.

Affected software

Ecosystem	Vendor	Product	Affected versions
Alpine:v3.22	–	nginx	< 1.28.3-r2 Fix: upgrade to 1.28.3-r2
Alpine:v3.23	–	nginx	< 1.28.3-r2 Fix: upgrade to 1.28.3-r2

Original title

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-...

Original description

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.

osv CVSS4.0 9.4

https://security.alpinelinux.org/vuln/CVE-2026-9256 Vendor Advisory