CVE-2026-9256: NGINX ngx_http_rewrite_module vulnerability
Last updated 6 June 2026
Other sources
NGINX ngxhttprewritemodule vulnerability
— Microsoft
NGINX Plus and NGINX Open Source have a vulnerability in the ngxhttprewritemodule 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.
— Launchpad
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
debian/nginxto a version that resolves this vulnerability.Fixed in 1.30.1-3
Event History
Frequently Asked Questions
What is the severity of CVE-2026-9256?
The severity of CVE-2026-9256 is high with a score of 8.1.
What types of NGINX products are affected by CVE-2026-9256?
CVE-2026-9256 affects both NGINX Plus and NGINX Open Source.
How do I fix CVE-2026-9256?
To fix CVE-2026-9256, you should update your NGINX installation to the latest version that addresses this vulnerability.
What is the nature of the vulnerability in CVE-2026-9256?
CVE-2026-9256 is a buffer overflow vulnerability in the ngx_http_rewrite_module involving regex patterns.
What can happen if CVE-2026-9256 is exploited?
Exploitation of CVE-2026-9256 could allow an attacker to execute arbitrary code on the affected NGINX server.