What is CVE-2026-4438?

CVE-2026-4438 is a medium-severity vulnerability in GNU Glibc, classified under Improper Input Validation. CVSS score: 5.4/10. Published 2026-03-20.

How severe is CVE-2026-4438?

Medium severity. CVSS v3 base score is 5.4 out of 10.

Improper input validation in GNU Glibc

CVE-2026-4438

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.

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

Published 2026-03-20 · last modified 2026-07-14.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.003 (14.9th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 15th percentile — 14.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: -0.001

Affected products

GNU Glibc
The GNU C Library Glibc — versions 2.34

Weakness classification (CWE)

References

3ff69d7a-14f2-4f67-a097-88dee7810d18 (Exploit, Patch, Issue Tracking)
0b142b55-0307-4c5a-b3c9-f314f3fb7c5e

Frequently asked questions

What is CVE-2026-4438?: CVE-2026-4438 is a medium-severity vulnerability in GNU Glibc, classified under Improper Input Validation. CVSS score: 5.4/10. Published 2026-03-20.
How severe is CVE-2026-4438?: Medium severity. CVSS v3 base score is 5.4 out of 10.