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CVE-2026-4438— gethostbyaddr and gethostbyaddr_r return invalid DNS hostnames

Quick assessment

Affected
The GNU C Library glibc
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.

GNU C Library是GNU社区的一种按照LGPL许可协议发布的开源免费的C语言编译程序。 GNU C library 2.34至2.43版本存在安全漏洞，该漏洞源于gethostbyaddr或gethostbyaddr_r函数可能返回无效的DNS主机名，违反DNS规范。

AI Predicted 5.9 Difficulty: Theoretical EPSS 0.25% · P15

Possible ATT&CK Techniques 1 AI

T1071 · Application Layer Protocol

Affected Version Matrix 1

VendorProduct Version RangeStatus
The GNU C Library glibc 2.34≤ 2.43 affected
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I. Basic Information for CVE-2026-4438

Vulnerability Information
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Vulnerability Title
gethostbyaddr and gethostbyaddr_r return invalid DNS hostnames
Source: CVE Program / CVE List V5
Vulnerability Description
Calling gethostbyaddr or gethostbyaddr_r with a configured nsswitch.conf that specifies the library's DNS backend in the GNU C library version 2.34 to version 2.43 could result in an invalid DNS hostname being returned to the caller in violation of the DNS specification.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
输入验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
GNU C Library 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
GNU C Library是GNU社区的一种按照LGPL许可协议发布的开源免费的C语言编译程序。 GNU C library 2.34至2.43版本存在安全漏洞，该漏洞源于gethostbyaddr或gethostbyaddr_r函数可能返回无效的DNS主机名，违反DNS规范。
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
The GNU C Library glibc 2.34 ~ 2.43 -

II. Public POCs for CVE-2026-4438

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III. Intelligence Information for CVE-2026-4438

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Other References for CVE-2026-4438 (1)

IV. Related Vulnerabilities

Same product: glibc
Same vendor: The GNU C Library
Same weakness: CWE-20

V. Comments for CVE-2026-4438

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