---
id: CVE-2026-4437
title: gethostbyaddr and gethostbyaddr_r may incorrectly handle DNS response
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, with a crafted response from the configured DNS server,
  result in …
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cvssSource: adp
cwe:
  - CWE-125
vendor: The GNU C Library
product: glibc
affected:
  - glibc >= 2.34 <= 2.43
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-03-23T15:10:34.650805Z'
published: '2026-03-20'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T01:12:09.122Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-4437'
references:
  - url: 'https://sourceware.org/bugzilla/show_bug.cgi?id=34014'
tags:
  - cve.org
epss: 0.00325
epssPercentile: 0.23881
ingestedAt: '2026-10-15T05:52:46.050Z'
---

## 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, with a crafted response from the configured DNS server, result in a violation of the DNS specification that causes the application to treat a non-answer section of the DNS response as a valid answer.

## Affected

- `glibc >= 2.34 <= 2.43`

## Remediation

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