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CVE Vulnerability Details :
CVE-2026-9256
PUBLISHED
More InfoOfficial Page
Assigner-f5
Assigner Org ID-9dacffd4-cb11-413f-8451-fbbfd4ddc0ab
View Known Exploited Vulnerability (KEV) details
Published At-22 May, 2026 | 14:11
Updated At-23 May, 2026 | 03:55
Rejected At-
▼CVE Numbering Authority (CNA)
NGINX ngx_http_rewrite_module vulnerability

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.

Affected Products
Vendor
F5, Inc.F5
Product
NGINX Plus
Modules
  • ngx_http_rewrite_module
Default Status
unknown
Versions
Affected
  • From 37.0 before 37.0.1.1 (custom)
  • From R36 before R36 P5 (custom)
  • From R32 before R32 P7 (custom)
Vendor
F5, Inc.F5
Product
NGINX Open Source
Modules
  • ngx_http_rewrite_module
Default Status
unaffected
Versions
Affected
  • From 1.31.0 before 1.31.1 (custom)
  • From 1.30.0 before 1.30.2 (custom)
  • From 0.1.17 before * (custom)
Problem Types
TypeCWE IDDescription
CWECWE-122CWE-122 Heap-based Buffer Overflow
Type: CWE
CWE ID: CWE-122
Description: CWE-122 Heap-based Buffer Overflow
Metrics
VersionBase scoreBase severityVector
3.18.1HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
4.09.2CRITICAL
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
Version: 3.1
Base score: 8.1
Base severity: HIGH
Vector:
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Version: 4.0
Base score: 9.2
Base severity: CRITICAL
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
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions

Configurations

Workarounds

Exploits

Credits

reporter
"F5 acknowledges Mufeed VH of Winfunc Research, Nebula Security (@nebusecurity), and Vexera AI for bringing this issue to our attention and following the highest standards of coordinated disclosure."
Timeline
EventDate
Replaced By

Rejected Reason

References
HyperlinkResource
https://my.f5.com/manage/s/article/K000161377
vendor-advisory
Hyperlink: https://my.f5.com/manage/s/article/K000161377
Resource:
vendor-advisory
▼Authorized Data Publishers (ADP)
1. CISA ADP Vulnrichment
Affected Products
Metrics
VersionBase scoreBase severityVector
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions

Configurations

Workarounds

Exploits

Credits

Timeline
EventDate
Replaced By

Rejected Reason

References
HyperlinkResource
2. CVE Program Container
Affected Products
Metrics
VersionBase scoreBase severityVector
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions

Configurations

Workarounds

Exploits

Credits

Timeline
EventDate
Replaced By

Rejected Reason

References
HyperlinkResource
http://www.openwall.com/lists/oss-security/2026/05/22/14
N/A
Hyperlink: http://www.openwall.com/lists/oss-security/2026/05/22/14
Resource: N/A
Details not found