CVE-2026-9256

CRITICAL EPSS 83.4%
Published May 22, 20261mo ago · Modified Jun 18, 20261w ago
9.2 CVSS 4.0
Critical
Find Similar
Published May 22, 2026 1mo ago
Last Modified Jun 18, 2026 1w ago

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 Details

Base Score
9.2
Exploitability
—
Impact
—
Vector string
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
Attack Vector Network
Attack Complexity High
Privileges Required None
User Interaction None
Scope X

Threat Intelligence

EPSS Exploit Probability
83.4% percentile
Exploit & Patch Status
No Known Exploit
No Patch Available

Weaknesses 1

CWE-122

Affected Products 5

VendorProductVersionRange
f5nginx_open_source*≥0.1.17  –  ≤0.9.7
f5nginx_open_source*≥1.0.0  –  ≤1.30.1
f5nginx_open_source1.31.0any
f5nginx_plus*≥37.0.0  –  <37.0.1.1
f5nginx_plus*≥r32  –  ≤r36

References 3

  • openwall.com http://www.openwall.com/lists/oss-security/2026/05/22/14
    Mailing ListThird Party Advisory
  • lists.debian.org https://lists.debian.org/debian-lts-announce/2026/06/msg00023.html
  • my.f5.com https://my.f5.com/manage/s/article/K000161377
    MitigationVendor Advisory

Remediation

No remediation data recorded yet

Check vendor advisories and the NVD entry for patch availability.