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CVE-2026-4438

gethostbyaddr and gethostbyaddr_r return invalid DNS hostnames

MEDIUM
5.4
CVSS Score
Published: March 20, 2026 at 07:59 PM UTC
Updated: October 15, 2026 at 01:12 AM UTC
5 products affected across 3 vendorsGlibcSIMATIC S7-1500 CPU 1518-4 Pn /dp MFP FirmwareSiplus S7-1500 CPU 1518-4 Pn /dp MFP Firmware

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Severity
MEDIUM5.4
Exploit prediction
EPSS 0.3%
SSVC
No known exploit

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 result in an invalid DNS hostname being returned to the caller in violation of the DNS specification.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Glibc· Gnu
95%
2.34 ≤ v ≤ 2.43
Glibc· Gnu C Library
60%
2.34 ≤ v ≤ 2.432.34
SIMATIC S7-1500 CPU 1518-4 Pn /dp MFP Firmware· Siemens
60%
V3.1.5 ≤ v < V3.1.63.1.5
Affected range stops below V3.1.6, so it looks safe — our inference, not a vendor statement
SIMATIC S7-1500 CPU 1518F 4 Pn /dp MFP Firmware· Siemens
60%
V3.1.5 ≤ v < V3.1.63.1.5
Affected range stops below V3.1.6, so it looks safe — our inference, not a vendor statement
Siplus S7-1500 CPU 1518-4 Pn /dp MFP Firmware· Siemens
60%
V3.1.5 ≤ v < V3.1.63.1.5
Affected range stops below V3.1.6, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (2)

ExploitIssue TrackingPatch
Source: cverecord
https://sourceware.org/bugzilla/show_bug.cgi?id=34015
Source: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
https://cert-portal.siemens.com/productcert/html/ssa-082556.html

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.4MEDIUM134c704f-9b21-4f2e-91b3-4a467353bcc0
Attack Vector
ADJACENT_NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-20CWE-88

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