CVE-2026-4438: CWE-20 Improper input validation in The GNU C Library glibc
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.
AI Analysis
Technical Summary
CVE-2026-4438 describes an input validation vulnerability (CWE-20) in glibc versions 2.34 through 2.43. When the functions gethostbyaddr or gethostbyaddr_r are called with a nsswitch.conf configuration specifying the DNS backend, the library may return an invalid DNS hostname that does not conform to DNS specifications. This improper validation could lead to potential issues in applications relying on these functions for hostname resolution.
Potential Impact
The vulnerability may cause applications using gethostbyaddr or gethostbyaddr_r to receive invalid DNS hostnames, potentially leading to incorrect behavior or security issues related to hostname validation. The CVSS score of 5.4 indicates a medium impact with limited confidentiality and integrity effects and no availability impact. There are no known exploits in the wild.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, users should review their use of gethostbyaddr and gethostbyaddr_r, especially in environments with DNS backend configured in nsswitch.conf, and consider additional validation of returned hostnames.
CVE-2026-4438: CWE-20 Improper input validation in The GNU C Library glibc
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.
CVSS v3.1
Score 5.4medium
Affected software
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-4438 describes an input validation vulnerability (CWE-20) in glibc versions 2.34 through 2.43. When the functions gethostbyaddr or gethostbyaddr_r are called with a nsswitch.conf configuration specifying the DNS backend, the library may return an invalid DNS hostname that does not conform to DNS specifications. This improper validation could lead to potential issues in applications relying on these functions for hostname resolution.
Potential Impact
The vulnerability may cause applications using gethostbyaddr or gethostbyaddr_r to receive invalid DNS hostnames, potentially leading to incorrect behavior or security issues related to hostname validation. The CVSS score of 5.4 indicates a medium impact with limited confidentiality and integrity effects and no availability impact. There are no known exploits in the wild.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, users should review their use of gethostbyaddr and gethostbyaddr_r, especially in environments with DNS backend configured in nsswitch.conf, and consider additional validation of returned hostnames.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- glibc
- Date Reserved
- 2026-03-19T19:55:44.639Z
- Cvss Version
- null
- State
- PUBLISHED
Threat ID: 69bda974e32a4fbe5fca0bbd
Added to database: 03/20/2026, 20:09:24 UTC
Last enriched: 07/15/2026, 11:24:02 UTC
Last updated: 08/02/2026, 07:17:57 UTC
Views: 234
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