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Message-ID: <f03868c2-2ef1-40a8-a469-fc6325b8a3c3@oracle.com>
Date: Fri, 22 May 2026 15:59:47 -0700
From: Alan Coopersmith <alan.coopersmith@...cle.com>
To: oss-security@...ts.openwall.com
Subject: NGINX ngx_http_rewrite_module buffer overflow
(CVE-2026-9256)
https://github.com/nginx/nginx/releases announces releases 1.31.1 and 1.30.2
containing a fix for a "buffer overflow vulnerability in the
ngx_http_rewrite_module (CVE-2026-9256)."
https://my.f5.com/manage/s/article/K000161377 gives this additional detail:
> 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. (CVE-2026-9256)
>
> Impact
>
> This vulnerability may allow remote attackers to cause a
> denial-of-service (DoS) on the NGINX system or to possibly trigger a
> code execution. There is no control plane exposure; this is a data
> plane issue only.
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