gethostbyaddr and gethostbyaddr_r return invalid DNS hostnames

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Summary

CVECVE-2026-4438
StatePUBLISHED
Assignerglibc
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-03-20 20:16:49 UTC
Updated2026-04-07 18:40:02 UTC
DescriptionCalling 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.

Risk And Classification

Primary CVSS: v3.1 5.4 MEDIUM from ADP

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

EPSS: 0.000300000 probability, percentile 0.084850000 (date 2026-04-07)

Problem Types: CWE-20 | CWE-88 | CWE-20 CWE-20 Improper input validation | CWE-88 CWE-88 Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')

VersionSourceTypeScoreSeverityVector
3.1ADPDECLARED5.4MEDIUMCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary5.4MEDIUMCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Adjacent
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Gnu Glibc All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA The GNU C Library Glibc affected 2.34 2.43 custom Not specified

References

ReferenceSourceLinkTags
sourceware.org/bugzilla/show_bug.cgi 3ff69d7a-14f2-4f67-a097-88dee7810d18 sourceware.org Exploit, Issue Tracking, Patch
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Antonio Maini (0rbitingZer0) - [email protected] (en)

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