Assessment
Why it matters
EPSS is 10.0%; technical severity is CVSS 9.2.
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.
Who should care
- Teams operating Debian Linux, Dos, Nginx Gateway Fabric +9 more
- Vulnerability and exposure management teams
- Security operations teams monitoring exploitation activity
Response plan
What I would do
- Confirm whether Debian Linux, Dos, Nginx Gateway Fabric +9 more is present in the environment.
- Identify affected versions and establish whether vulnerable services are exposed or reachable.
- F5 Security advisory K000161377
- Review relevant security telemetry for evidence of attempted or successful exploitation.
- Document the remediation decision and track it to verified completion.
Treatment intelligence
Remediation intelligence
Vendor sources are listed before government and third-party guidance. Confirm product applicability and change prerequisites before deployment.
Technical details
- CVSS vector
- CVSS: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/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
- CWE
- CWE-122
- Affected versions
- Debian Debian Linux (Version 11.0); F5 Dos (Start Including 4.3.0, End Including 4.7.0 | Version 4.9.0); F5 Nginx Gateway Fabric (Start Including 1.3.0, End Including 1.6.2 | Start Including 2.0.0, End Excluding 2.6.2); F5 Nginx Ingress Controller (Start Including 3.5.0, End Including 3.7.2 | Start Including 4.0.0, End Including 4.0.1 | Start Including 5.0.0, End Excluding 5.4.3); F5 Nginx Instance Manager (Start Including 2.17.0, End Excluding 2.22.1); F5 Nginx Open Source (Start Including 0.1.17, End Including 0.9.7 | Start Including 1.0.0, End Excluding 1.30.2 | Version 1.31.0); F5 Nginx Plus (Start Including r33, End Excluding r36 | Version 37.0.0.1 | Version r32 | Version r32); F5 Waf (Start Including 4.10.0, End Including 4.16.0 | Start Including 5.2.0, End Including 5.8.0 | Start Including 5.9.0, End Including 5.13.0)
- Fixed versions
- F5 Nginx Gateway Fabric (Fixed from 2.6.2); F5 Nginx Ingress Controller (Fixed from 5.4.3); F5 Nginx Instance Manager (Fixed from 2.22.1); F5 Nginx Open Source (Fixed from 1.30.2); F5 Nginx Plus (Fixed from r36); Redhat Update Infrastructure (Fixed from 5.2)
- Published
- 22 May 2026
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
Signal timeline
- CVE published
- Latest EPSS score: 10.0%
- Signal calculated at 19
External references
- Debian Third-party advisory Msg00023
- Red Hat Third-party advisory RHSA-2026:20351
- Red Hat Third-party advisory RHSA-2026:28212
- Red Hat Third-party advisory RHSA-2026:28921
- Red Hat Third-party advisory RHSA-2026:28973
- Red Hat Third-party advisory RHSA-2026:29151
- Red Hat Third-party advisory RHSA-2026:29874
- Red Hat Third-party advisory RHSA-2026:33313
- Red Hat Third-party advisory RHSA-2026:44481
- Red Hat Third-party advisory Show Bug.cgi
- Openwall Technical reference