---
id: CVE-2026-4438
title: gethostbyaddr and gethostbyaddr_r return invalid DNS hostnames
summary: >-
  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 v…
severity: medium
cvss: 5.4
cvssVector: 'CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N'
cvssSource: adp
cwe:
  - CWE-20
vendor: The GNU C Library
product: glibc
affected:
  - glibc >= 2.34 <= 2.43
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-03-23T15:06:13.636418Z'
published: '2026-03-20'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T01:12:10.681Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-4438'
references:
  - url: 'https://sourceware.org/bugzilla/show_bug.cgi?id=34015'
tags:
  - cve.org
epss: 0.00316
epssPercentile: 0.22853
ingestedAt: '2026-10-15T05:52:46.049Z'
---

## Overview

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.

## Affected

- `glibc >= 2.34 <= 2.43`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.