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CVE-2026-30923— libModSecurity3 denial of service via segfault when using t:hexDecode on single-character query strings

Quick assessment

Affected
owasp-modsecurity ModSecurity
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Modsecurity是OWASP ModSecurity开源的一个Web流量安全处理库。 Modsecurity 3.0.15之前版本存在缓冲区错误漏洞，该漏洞源于使用t:hexDecode转换的规则检查包含单个字符的查询字符串参数时发生段错误，攻击者可以利用此漏洞崩溃工作进程导致拒绝服务。

AI Predicted 7.5 Difficulty: Easy EPSS 0.52% · P42

Affected Version Matrix 1

VendorProduct Version RangeStatus
owasp-modsecurity ModSecurity < 3.0.15 affected
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I. Basic Information for CVE-2026-30923

Vulnerability Information
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Vulnerability Title
libModSecurity3 denial of service via segfault when using t:hexDecode on single-character query strings
Source: CVE Program / CVE List V5
Vulnerability Description
ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. Libmodsecurity is one component of the ModSecurity v3 project. A segmentation fault occurs when a rule using the t:hexDecode transformation inspects a query string parameter containing a single character. An attacker can exploit this to crash worker processes, causing a denial of service. Service resumes once the attack stops as worker processes recover from the segfault. All versions before 3.0.15 of libModSecurity3 are affected. This has been patched in version 3.0.15.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存读
Source: CVE Program / CVE List V5
Vulnerability Title
Modsecurity 缓冲区错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Modsecurity是OWASP ModSecurity开源的一个Web流量安全处理库。 Modsecurity 3.0.15之前版本存在缓冲区错误漏洞，该漏洞源于使用t:hexDecode转换的规则检查包含单个字符的查询字符串参数时发生段错误，攻击者可以利用此漏洞崩溃工作进程导致拒绝服务。
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
owasp-modsecurity ModSecurity < 3.0.15 -

II. Public POCs for CVE-2026-30923

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III. Intelligence Information for CVE-2026-30923

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Vendor Advisories for CVE-2026-30923 (1)

Vendor Pages for CVE-2026-30923 (1)

IV. Related Vulnerabilities

Same product: ModSecurity
Same vendor: owasp-modsecurity
Same weakness: CWE-125

V. Comments for CVE-2026-30923

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