CVE-2026-9256
NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module.
Does this matter?
EPSS puts the probability of exploitation in the next 30 days at 10.9%, higher than 96% of all known CVEs. Patch or mitigate before the next change window.
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.
- CVSS 4.0
- 9.2 CRITICALCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
- EPSS
- 10.86% probability · 96th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-122
- Affected
- f5/nginx open source · f5/nginx plus · f5/dos · f5/nginx gateway fabric · f5/nginx ingress controller · f5/nginx instance manager · f5/waf · redhat/discovery · redhat/hardened images · redhat/update infrastructure · debian/debian linux · redhat/enterprise linux
- Source
- f5sirt@f5.com
References
- https://my.f5.com/manage/s/article/K000161377Mitigation, Vendor Advisory
- http://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
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.