CVE-2026-9256

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.

How to fix CVE-2026-9256

To remediate CVE-2026-9256, upgrade the affected package to a fixed version below.

• —upgrade to 1.28.3-r2 or later
• —upgrade to 1.24.0 or later
• —upgrade to 2.2.1 or later
• —no fix listed

Is CVE-2026-9256 being exploited?

Low — EPSS is 0.2%, meaning exploitation activity has not been observed at scale.

Affected packages (4)

• from 0, < 1.28.3-r2
• >= 0.1.17, < 1.24.0, >= 1.30.0, < 1.30.2, >= 1.31.0, < 1.31.1
• >= 0.1.17, < 2.2.1
• from 0

CVSS scores

References (5)

• ADVISORYsecurity.alpinelinux.org/vuln/CVE-2026-9256
• ADVISORYsecurity-tracker.debian.org/tracker/CVE-2026-9256
• WEBmy.f5.com/manage/s/article/K000161377
• WEBnvd.nist.gov/vuln/detail/CVE-2026-9256
• WEB