CVE-2026-4437 | gethostbyaddr and gethostbyaddr_r may incorrectly handle DNS response

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, 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.

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-2026-4437 is rated Exploit Available (50.4/100): CVSS High severity, with low exploitation likelihood (EPSS 0.05%). 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-2026-4437

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

Exploit prediction scoring system (EPSS) score for CVE-2026-4437

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 2026-04-21 0.05% 0.05% +0.00%
2 2026-04-08 0.05% 0.05% -0.01%
3 2026-03-26 — 0.05% —

Full EPSS history (4 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-4437

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
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:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2026-4437

OS Trackers for CVE-2026-4437

vendor priority summary link
debian unimportant CVE-2026-4437 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-2026-4437
redhat medium — https://access.redhat.com/security/cve/CVE-2026-4437
suse medium CVE-2026-4437 severity moderate: SUSE including 95 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, …), 365 product×package rows across 79 product lines (Container private-registry/harbor-core, Container private-registry/harbor-exporter, … (79 product lines)): Known Not Affected 177, Fixed 175, First Fixed 13. https://www.suse.com/security/cve/CVE-2026-4437/
ubuntu medium CVE-2026-4437 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-2026-4437

Affected software / configurations for CVE-2026-4437

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

References for CVE-2026-4437

URL Tags
https://sourceware.org/bugzilla/show_bug.cgi?id=34014 Exploit Issue Tracking Patch
cvelogic Threat Intelligence