GNU C Library up to 2.43 nsswitch.conf gethostbyaddr/gethostbyaddr_r input validation

Summaryinfo

A vulnerability described as problematic has been identified in GNU C Library up to 2.43. This affects the function gethostbyaddr/gethostbyaddr_r of the file nsswitch.conf. Such manipulation leads to input validation. This vulnerability is uniquely identified as CVE-2026-4438. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability was found in GNU C Library up to 2.43 and classified as problematic. Affected by this issue is the function gethostbyaddr/gethostbyaddr_r of the file nsswitch.conf. The manipulation with an unknown input leads to a input validation vulnerability. Using CWE to declare the problem leads to 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. Impacted is integrity. CVE summarizes:

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.

The advisory is shared for download at sourceware.org. This vulnerability is handled as CVE-2026-4438 since 03/19/2026. The exploitation is known to be difficult. The attack may be launched remotely. No form of authentication is required for exploitation. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 06/20/2026).

The vulnerability scanner Nessus provides a plugin with the ID 303236 (Linux Distros Unpatched Vulnerability : CVE-2026-4438), which helps to determine the existence of the flaw in a target environment.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the databases at Tenable (303236), EUVD (EUVD-2026-13798) and CERT Bund (WID-SEC-2026-0817). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Affected

• Google Container-Optimized OS
• Red Hat Enterprise Linux
• SUSE Linux
• Oracle Linux
• NetApp ActiveIQ Unified Manager
• SUSE openSUSE
• RESF Rocky Linux
• IBM MQ
• Open Source GNU libc

Productinfo

Type

• Software Library

Vendor

• GNU

Name

• C Library

Version

• 2.0
• 2.1
• 2.2
• 2.3
• 2.4
• 2.5
• 2.6
• 2.7
• 2.8
• 2.9
• 2.10
• 2.11
• 2.12
• 2.13
• 2.14
• 2.15
• 2.16
• 2.17
• 2.18
• 2.19
• 2.20
• 2.21
• 2.22
• 2.23
• 2.24
• 2.25
• 2.26
• 2.27
• 2.28
• 2.29
• 2.30
• 2.31
• 2.32
• 2.33
• 2.34
• 2.35
• 2.36
• 2.37
• 2.38
• 2.39
• 2.40
• 2.41
• 2.42
• 2.43

License

• open-source

Website

• Vendor: https://www.gnu.org/

CPE 2.3info

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CPE 2.2info

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Entryinfo

VulDB is the best source for vulnerability data and more expert information about this specific topic.

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