CVE-2026-9256
8.1 · HIGHOverview
CVE-2026-9256 is a high-severity vulnerability affecting f5 nginx_open_source. It was published on May 22, 2026 and has a CVSS 3.1 base score of 8.1 (HIGH).
This vulnerability has a CVSS 3.1 base score of 8.1, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical 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.
Remediation
Check the references section for vendor advisories and patches from f5. Update nginx_open_source to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| f5 | nginx_open_source | 0.1.17 | Affected |
| f5 | nginx_plus | >= r33, < r36 | Affected |
| f5 | dos | 4.3.0 | Affected |
| f5 | nginx_gateway_fabric | 1.3.0 | Affected |
| f5 | nginx_ingress_controller | 3.5.0 | Affected |
| f5 | nginx_instance_manager | >= 2.17.0, < 2.22.1 | Affected |
| f5 | waf | 4.10.0 | Affected |
| redhat | update_infrastructure | >= 5.0, < 5.2 | Affected |
References
Frequently Asked Questions
What is CVE-2026-9256?
CVE-2026-9256 is a high-severity vulnerability affecting f5 nginx_open_source. It was published on May 22, 2026 and has a CVSS 3.1 base score of 8.1 (HIGH).
How severe is CVE-2026-9256?
This vulnerability has a CVSS 3.1 base score of 8.1, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2026-9256?
Check the references section for vendor advisories and patches from f5. Update nginx_open_source to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-9256?
CyberStrike's AI-powered security agents can automatically detect CVE-2026-9256 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
AI agents map your attack surface to find vulnerabilities like this one.
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