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CVE-2026-9256

F5 Nginx Open Source

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.

Exploitation status

  • A vendor advisory or patch reference has been published.

What the metrics mean

  • It is reachable over a network, without needing local access.
  • For an attacker who can reach it, exploitation depends on conditions outside the attacker's control.
  • To exploit it, no account is needed.
  • Beyond that, no action by a user is required.

Scoring

CVSS
8.1 (v3.1)
Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS v4
9.2
Weakness
CWE-122
Assigned by
f5sirt@f5.com

Dates

Published
2026-05-22
Last modified
2026-08-25
Sources
NVD

Affected products

  • F5 Nginx Open Source0.1.17 - 0.9.7, 1.0.0 - 1.30.2, 1.31.0
  • F5 Nginx Plusr33 - r36, 37.0.0.1, r32, r36
  • F5 Dos4.3.0 - 4.7.0, 4.9.0
  • F5 Nginx Gateway Fabric1.3.0 - 1.6.2, 2.0.0 - 2.6.2
  • F5 Nginx Ingress Controller3.5.0 - 3.7.2, 4.0.0 - 4.0.1, 5.0.0 - 5.4.3
  • F5 Nginx Instance Manager2.17.0 - 2.22.1
  • F5 Waf4.10.0 - 4.16.0, 5.2.0 - 5.8.0, 5.9.0 - 5.13.0
  • Redhat Discoveryall versions
  • Redhat Hardened Imagesall versions
  • Redhat Update Infrastructure5.0 - 5.2
  • Debian Debian Linux11.0
  • Redhat Enterprise Linux8.0, 9.0, 10.0

As listed in the NVD configuration data. Not a statement about your estate.

References