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National Vulnerability Database

National Vulnerability Database

NVD

National Vulnerability Database
  1. Vulnerabilities

CVE-2026-9256 Detail

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.


Metrics

 
NVD enrichment efforts reference publicly available information to associate vector strings. CVSS information contributed by other sources is also displayed.
CVSS 4.0 Severity and Vector Strings:

NIST CVSS score
NIST: NVD
N/A
NVD assessment not yet provided.

Nist CVSS score does not match with CNA score
CNA:  F5 Networks
CVSS-B 9.2 CRITICAL
Vector:  CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

References to Advisories, Solutions, and Tools

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URL Source(s) Tag(s)
https://my.f5.com/manage/s/article/K000161377 F5 Networks

Weakness Enumeration

CWE-ID CWE Name Source
CWE-122 Heap-based Buffer Overflow F5 Networks  

Change History

1 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2026-9256
NVD Published Date:
05/22/2026
NVD Last Modified:
05/22/2026
Source:
F5 Networks