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CVE-2026-9256— NGINX ngx_http_rewrite_module vulnerability

Quick assessment

Affected
F5 NGINX Plus
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

F5 NGINX Plus和F5 NGINX Open Source都是美国F5公司的产品。F5 NGINX Plus是一个基于软件的应用程序交付平台。F5 NGINX Open Source是一个高性能Web服务器、反向代理服务器、负载均衡器和API网关。 F5 NGINX Plus和F5 NGINX Open Source存在安全漏洞，该漏洞源于ngx_http_rewrite_module模块中重写指令使用具有重叠PCRE捕获的正则表达式模式时，可能导致堆缓冲区溢出，造成工作进程重启，并在ASLR禁

CVSS 8.1 · High EPSS 2.70% · P85

Affected Version Matrix 6

VendorProduct Version RangeStatus
F5 NGINX Open Source 1.31.0< 1.31.1 affected
1.30.0< 1.30.2 affected
0.1.17≤ 0.9.7 affected
F5 NGINX Plus 37.0< 37.0.1.1 affected
R36< R36 P5 affected
R32< R32 P7 affected
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I. Basic Information for CVE-2026-9256

Vulnerability Information
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Vulnerability Title
NGINX ngx_http_rewrite_module vulnerability
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
堆缓冲区溢出
Source: CVE Program / CVE List V5
Vulnerability Title
F5 NGINX Plus和F5 NGINX Open Source 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
F5 NGINX Plus和F5 NGINX Open Source都是美国F5公司的产品。F5 NGINX Plus是一个基于软件的应用程序交付平台。F5 NGINX Open Source是一个高性能Web服务器、反向代理服务器、负载均衡器和API网关。 F5 NGINX Plus和F5 NGINX Open Source存在安全漏洞，该漏洞源于ngx_http_rewrite_module模块中重写指令使用具有重叠PCRE捕获的正则表达式模式时，可能导致堆缓冲区溢出，造成工作进程重启，并在ASLR禁
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
F5 NGINX Plus 37.0 ~ 37.0.1.1 -
F5 NGINX Open Source 1.31.0 ~ 1.31.1 -

II. Public POCs for CVE-2026-9256

# POC Description Source Link Shenlong Link
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default-local-qwen3.6 · 13435 chars
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III. Intelligence Information for CVE-2026-9256

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Vendor Advisories for CVE-2026-9256 (1)

IV. Related Vulnerabilities

Same product: NGINX Plus
Same vendor: F5
Same weakness: CWE-122

V. Comments for CVE-2026-9256

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