CVE-2026-4438
Received Received - Intake
DNS Spoofing via gethostbyaddr in GNU C Library

Publication date: 2026-03-20

Last updated on: 2026-04-07

Assigner: GNU C Library

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.
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Meta Information
Published
2026-03-20
Last Modified
2026-04-07
Generated
2026-06-16
AI Q&A
2026-03-20
EPSS Evaluated
2026-06-15
NVD
CVE-2026-4438
EUVD
EUVD-2026-13798
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
gnu glibc From 2.34 (inc) to 2.43 (inc)
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Exploitability
CWE
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KEV
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CWE ID Description
CWE-88 The product constructs a string for a command to be executed by a separate component in another control sphere, but it does not properly delimit the intended arguments, options, or switches within that command string.
CWE-20 The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
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Executive Summary

This vulnerability occurs when the functions gethostbyaddr or gethostbyaddr_r are called in the GNU C library versions 2.34 to 2.43 with a configured nsswitch.conf that specifies the library's DNS backend. Under these conditions, the functions could return an invalid DNS hostname to the caller, which violates the DNS specification.

Impact Analysis

The impact of this vulnerability is that applications relying on gethostbyaddr or gethostbyaddr_r for hostname resolution may receive invalid DNS hostnames. This could lead to incorrect hostname information being used in network communications or logging, potentially causing failures, misrouting, or security issues related to hostname validation.

Compliance Impact

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Detection Guidance

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