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HIGH

CVE-2026-9256

NGINX ngx_http_rewrite_module vulnerability

CVSS v3

8.1

HIGH

EPSS Score

2.7 %

exploit probability, as of 2026-10-19

CISA KEV

No

known exploited

Exploitation

none

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • nginxBitnamifrom 0.1.17 · fixed in 1.24.0
  • nginx-gatewayBitnamifrom 0.1.17 · fixed in 2.2.1
  • nginxAlmaLinux:10all versions · fixed in 2:1.26.3-6.el10_2.4and 9 other packages
  • nginxAlmaLinux:9all versions · fixed in 2:1.26.3-9.module_el9.8.0+260+95b8e5ed.1and 9 other packages
  • nginxAlmaLinux:8all versions · fixed in 1:1.24.0-3.module_el8.10.0+4200+fea3b4c7.2.alma.1and 8 other packages

Vendor advisories

  • CVE-2026-9256 Red Hat Product Security402 products fixed · 1 known affected

    nginx: ngx_http_rewrite_module: code execution and denial of service

    insights-proxy/insights-proxy-container-rhel9 as a component of Red Hat Lightspeed proxy 1

  • RHSA-2026:58981 Red Hat Product Security2 products fixed

    Red Hat Security Advisory: Red Hat Update Infrastructure 5.3 Technology Preview security update

  • RHSA-2026:44481 Red Hat Product Security3 products fixed

    Red Hat Security Advisory: Red Hat Update Infrastructure 5.2 security update

  • RHSA-2026:33313 Red Hat Product Security2 products fixed

    Red Hat Security Advisory: A Subscription Management tool for finding and reporting Red Hat product usage

  • RHSA-2026:29874 Red Hat Product Security99 products fixed

    Red Hat Security Advisory: nginx security update

  • RHSA-2026:29151 Red Hat Product Security67 products fixed

    Red Hat Security Advisory: nginx:1.26 security update

4 more advisories

Full record on NVD

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.

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
2026-06-01
Last Modified
2026-08-11
MSRC Title
NGINX ngx_http_rewrite_module vulnerability

Frequently asked questions

What is 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.

Is CVE-2026-9256 actively exploited?

Active exploitation of CVE-2026-9256 has not been confirmed. Its EPSS score was 2.7% on 2026-10-19, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-9256?

CVE-2026-9256 has a CVSS v3 base score of 8.1 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.

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