CVE-2026-4438 | gethostbyaddr and gethostbyaddr_r return invalid DNS hostnames

Exp

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.

Published: 2026-03-20 Last update: 2026-04-07 Assigner: 3ff69d7a-14f2-4f67-a097-88dee7810d18 Source: 3ff69d7a-14f2-4f67-a097-88dee7810d18
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-4438 is rated Exploit Available (50/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.06%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2026-4438

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2026-4438

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-20 0.04% 0.06% +0.02%
2 2026-03-21 — 0.04% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-4438

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.4 3.1 MEDIUM
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N Click to expand
Attack vector (AV:A)
Attacker has to be nearby on the network—same office, same link, that vibe—not the whole wide internet.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 2.5 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2026-4438

OS Trackers for CVE-2026-4438

vendor priority summary link
debian unimportant CVE-2026-4438 unimportant priority: Debian including 1 source packages (glibc), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2026-4438
redhat low — https://access.redhat.com/security/cve/CVE-2026-4438
suse medium CVE-2026-4438 severity moderate: SUSE including 94 source package names (1.1.2-2.17:glibc-2.38-150600.14.46.1, 1.1.2-2.18:glibc-2.38-150600.14.46.1, …), 363 product×package rows across 77 product lines (Container private-registry/harbor-core, Container private-registry/harbor-exporter, … (77 product lines)): Fixed 175, Known Not Affected 175, First Fixed 13. https://www.suse.com/security/cve/CVE-2026-4438/
ubuntu medium CVE-2026-4438 medium priority: Ubuntu including 2 source packages (eglibc, glibc), 12 status rows across 8 suites (bionic, focal, jammy, noble, questing, trusty, upstream, xenial): needs-triage 9, DNE 3. https://ubuntu.com/security/CVE-2026-4438

Affected software / configurations for CVE-2026-4438

Vendor Product Version Raw CPE
gnu glibc >= 2.34, <= 2.43 cpe:2.3:a:gnu:glibc:*:*:*:*:*:*:*:*

References for CVE-2026-4438

URL Tags
https://sourceware.org/bugzilla/show_bug.cgi?id=34015 Exploit Issue Tracking Patch
cvelogic Threat Intelligence