CVE-2026-9256
As of 2026-05-28, CVE-2026-9256 is a CVSS 8.1 (HIGH-severity) vulnerability. EPSS exploitation probability 0.2%. Threadlinqs Intelligence tracks 2 threats exploiting it.
Last updated: 2026-05-28
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 v3 vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Weaknesses (CWE)
CWE-122
Threats tracking this CVE
- F5 Patches Multiple NGINX Vulnerabilities: Heap Overflow, Memory Disclosure, and Use-After-Free (CVE-2026-42533, CVE-2026-60005, CVE-2026-56434) — CRITICAL
- Nginx-poolslip CVE-2026-9256 — Pre-Auth Heap Buffer Overflow in NGINX ngx_http_rewrite_module (Patch Bypass of CVE-2026-42945 'NGINX Rift') — CRITICAL
References
← all vulnerabilities · Markdown version · Threadlinqs Intelligence
Enriched from CVE.org, NVD (this product uses the NVD API but is not endorsed or certified by the NVD), FIRST EPSS, CISA KEV, and GitHub Security Advisories.