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GNU C Library (glibc) CVE-2026-5435

| EUVDEUVD-2026-26036 HIGH
Out-of-bounds Write (CWE-787)
2026-04-28 3ff69d7a-14f2-4f67-a097-88dee7810d18
7.3
CVSS 3.1 · Vendor: 3ff69d7a-14f2-4f67-a097-88dee7810d18
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Severity by source

Vendor (3ff69d7a-14f2-4f67-a097-88dee7810d18) PRIMARY
7.3 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
SUSE
HIGH
qualitative
Red Hat
5.9 MEDIUM
qualitative

Primary rating from Vendor (3ff69d7a-14f2-4f67-a097-88dee7810d18).

CVSS VectorVendor: 3ff69d7a-14f2-4f67-a097-88dee7810d18

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
Low

Lifecycle Timeline

6
Re-analysis Queued
Apr 28, 2026 - 20:38 vuln.today
cvss_changed
Analysis Generated
Apr 28, 2026 - 16:23 vuln.today
CVSS changed
Apr 28, 2026 - 16:22 NVD
7.3 (HIGH)
EUVD ID Assigned
Apr 28, 2026 - 13:22 euvd
EUVD-2026-26036
Analysis Generated
Apr 28, 2026 - 13:22 vuln.today
CVE Published
Apr 28, 2026 - 13:19 nvd
HIGH 7.3

DescriptionCVE.org

The deprecated functions ns_printrrf, ns_printrr and fp_nquery in the GNU C Library version 2.2 and newer fail to enforce the caller-supplied buffer length, and can result in an out-of-bounds write when printing TSIG records.

AnalysisAI

Out-of-bounds write in GNU C Library 2.2+ allows remote unauthenticated attackers to corrupt memory and potentially execute arbitrary code through specially crafted TSIG DNS records processed by deprecated ns_printrrf, ns_printrr, or fp_nquery functions. While these functions are deprecated, any application still using them for DNS record printing remains vulnerable to network-based attacks with low complexity and no authentication barriers. No public exploit identified at time of analysis, but the deprecated status suggests limited real-world exposure despite the network attack vector.

Technical ContextAI

This vulnerability affects deprecated DNS resolver library functions (ns_printrrf, ns_printrr, fp_nquery) in GNU C Library versions 2.2 and newer. These functions are part of glibc's BIND compatibility layer for DNS operations. The root cause is CWE-787 (Out-of-bounds Write), where the functions fail to properly enforce caller-supplied buffer length constraints when formatting TSIG (Transaction Signature) resource records for printing. TSIG is a DNS protocol extension defined in RFC 2845 used for authenticating DNS messages. The buffer overflow occurs during the string formatting operations when these functions process TSIG record data without validating that the output remains within the allocated buffer boundaries. The affected CPE is cpe:2.3:a:gnu:glibc:2.2:*:*:*:*:*:*:* and all subsequent versions through current releases, representing decades of potentially vulnerable installations across Linux and Unix-like systems.

RemediationAI

Primary remediation is to upgrade to a patched glibc version once released by the GNU C Library project, monitoring the sourceware bugzilla #34033 for patch availability announcements. Since the affected functions are deprecated, the recommended long-term fix is to refactor application code to remove all calls to ns_printrrf, ns_printrr, and fp_nquery, replacing them with modern DNS record handling functions from the glibc resolver library or alternative DNS libraries. As an immediate compensating control, audit your codebase for use of these three functions using grep or static analysis tools; if not used, no action required beyond eventual OS-level glibc update. If functions are in use, implement strict input validation on any DNS record data before passing to these functions, specifically limiting TSIG record size and content, though this is complex and error-prone compared to removing deprecated function calls entirely. Organizations using network-based DNS services should consider restricting which systems can receive TSIG records if the vulnerable functions are confirmed in use, though this may break legitimate DNS authentication workflows. Advisory and patch status at https://inbox.sourceware.org/libc-announce/7a655d55-276f-41fe-b550-feb3ebb2ce91@redhat.com/.

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Vendor StatusVendor

SUSE

Severity: High
Product Status
SLES15-SP5-CHOST-BYOS-SAP-CCloud Fixed
SLES15-SP6-CHOST-BYOS Fixed
SLES15-SP6-CHOST-BYOS-Aliyun Fixed
SLES15-SP6-CHOST-BYOS-Azure Fixed
SLES15-SP6-CHOST-BYOS-EC2 Fixed

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CVE-2026-5435 vulnerability details – vuln.today

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