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VulnerabilityPublished Updated

CVE-2026-4437: The GNU C Library glibc · Out-of-bounds Read

Affects The GNU C Library glibcSource CVE Database V5

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Not known to be exploited · CVSS 7.5 High.

Data as of 1 Nov 2026, 22:58 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.3% chance of exploitation in 30 days – higher than 27% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 20 Mar 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 1 Nov 2026.

What to do

Affected software

ProductAffectedFixed in
The GNU C LibraryglibcAffected
  • >=2.34 <=2.43
Fixed in–
Debiandebian/glibcpkg:deb/debian/glibcOther threatsAffected
  • =2.34
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Until an official fix is available, consider avoiding configurations that use the DNS backend in nsswitch.conf with affected glibc versions or implement network-level protections to filter malicious DNS responses.

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, 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.

References

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