CVE-2026-9256

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.

• CWE-122
• CWE-122

• https://my.f5.com/manage/s/article/K000161377Mitigation, Vendor Advisory
• https://www.openwall.com/lists/oss-security/2026/05/22/14Mailing List
• https://lists.debian.org/debian-lts-announce/2026/06/msg00023.htmlMailing List, Third Party Advisory
• https://access.redhat.com/errata/RHSA-2026:20351Third Party Advisory
• https://access.redhat.com/errata/RHSA-2026:28212Third Party Advisory
• https://access.redhat.com/errata/RHSA-2026:28921Third Party Advisory
• https://access.redhat.com/errata/RHSA-2026:28973Third Party Advisory
• https://access.redhat.com/errata/RHSA-2026:29151Third Party Advisory
• https://access.redhat.com/errata/RHSA-2026:29874Third Party Advisory
• https://access.redhat.com/errata/RHSA-2026:33313Third Party Advisory
• https://access.redhat.com/errata/RHSA-2026:44481Third Party Advisory
• https://access.redhat.com/errata/RHSA-2026:58981
• https://access.redhat.com/security/cve/CVE-2026-9256Third Party Advisory
• https://bugzilla.redhat.com/show_bug.cgi?id=2480746Issue Tracking, Third Party Advisory
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-9256.jsonThird Party Advisory

Published

May 22, 2026

Last Modified

Aug 25, 2026

Status

Modified

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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