High severity · published May 22, 2026
CVE-2026-9256
NGINX ngx_http_rewrite_module vulnerability
8.1
CVSS
10.9%
EPSS
No
On KEV
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 vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)10.9% · higher than 96% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
NO
NGINX Open Source · F5
1.31.0 before 1.31.1; 1.30.0 before 1.30.2; 0.1.17 through 0.9.7 · source: vendor, NVD
NP
NGINX Plus · F5
37.0 before 37.0.1.1; R36 before R36 P5; R32 before R32 P7 · source: vendor, NVD
DL
Debian Linux · Debian
11.0 · source: NVD
DI
Discovery · Redhat
All versions, or not specified · source: NVD
DO
Dos · F5
4.3.0 through 4.7.0; 4.9.0 · source: NVD
EL
Enterprise Linux · Redhat
8.0; 9.0; 10.0 · source: NVD
HI
Hardened Images · Redhat
All versions, or not specified · source: NVD
NG
Nginx Gateway Fabric · F5
1.3.0 through 1.6.2; 2.0.0 before 2.6.2 · source: NVD
NI
Nginx Ingress Controller · F5
3.5.0 through 3.7.2; 4.0.0 through 4.0.1; 5.0.0 before 5.4.3 · source: NVD
NI
Nginx Instance Manager · F5
2.17.0 before 2.22.1 · source: NVD
UI
Update Infrastructure · Redhat
5.0 before 5.2 · source: NVD
WA
Waf · F5
4.10.0 through 4.16.0; 5.2.0 through 5.8.0; 5.9.0 through 5.13.0 · source: NVD
Affected product
NO
NGINX Open Source
F5
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