CVE-2026-4437Network attack vector

Reverse-DNS result obfuscation via section-boundary crossing

Published Mar 20, 2026 · Updated Mar 20, 2026

Improper DNS response handling in GNU Project glibc 2.34 through 2.43 allows attackers to return an incorrect hostname via crafted DNS data. The getanswer_ptr function can cross the answer-section boundary when all answer records are skipped, then accept an invalid PTR record from the next section. Attackers must be network adjacent or control the configured DNS server; the result can obscure reverse-DNS data from monitoring, but the associated connections remain visible.

CVSS severity7.5
High
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper DNS response handling in GNU Project glibc 2.34 through 2.43 allows attackers to return an incorrect hostname via crafted DNS data. The getanswer_ptr function can cross the answer-section boundary when all answer records are skipped, then accept an invalid PTR record from the next section. Attackers must be network adjacent or control the configured DNS server; the result can obscure reverse-DNS data from monitoring, but the associated connections remain visible.

The record

CVE
CVE-2026-4437
Published
Mar 20, 2026
Updated
Mar 20, 2026
Vendor
The GnuPG Project
Product
glibc
Classifications
CWE-125, CAPEC-142, T1565.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 20, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 20, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.34 <=2.43

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The GnuPG Project · glibcversion=2.34 <=2.43

Published CVSS scores

7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-125Out-of-bounds Read
CAPEC-142DNS Cache Poisoning
T1565.002Transmitted Data Manipulation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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