GNU C Library up to 2.33 DNS Response ns_printrrf/ns_printrr/fp_nquery buffer over-read

Summaryinfo

A vulnerability classified as problematic was found in GNU C Library up to 2.33. Affected is the function ns_printrrf/ns_printrr/fp_nquery of the component DNS Response Handler. Such manipulation leads to buffer over-read. This vulnerability is documented as CVE-2026-6238. The attack can be executed remotely. There is not any exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in GNU C Library up to 2.33 and classified as problematic. Affected by this issue is the function ns_printrrf/ns_printrr/fp_nquery of the component DNS Response Handler. The manipulation with an unknown input leads to a buffer over-read vulnerability. Using CWE to declare the problem leads to CWE-126. The product reads from a buffer using buffer access mechanisms such as indexes or pointers that reference memory locations after the targeted buffer. Impacted is confidentiality, integrity, and availability. CVE summarizes:

The deprecated functions ns_printrrf, ns_printrr and fp_nquery in the GNU C Library version 2.0.1 to version 2.43 fail to validate the RDATA content against the RDATA length in a DNS response when processing A6, CERT, LOC, TKEY or TSIG records, which may allow an attacker to craft a DNS response, causing a target application to crash or read uninitialized memory. These functions are for application debugging only and hence not in the path of code executed by the DNS resolver. Further, they have been deprecated since version 2.34 and should not be used by any new applications. Applications should consider porting away from these interfaces since they may be removed in future versions.

The advisory is shared for download at sourceware.org. This vulnerability is handled as CVE-2026-6238 since 04/13/2026. The exploitation is known to be difficult. The attack may be launched remotely. No form of authentication is required for exploitation. There are known technical details, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 312242 (Fedora 43 : glibc (2026-4b7780802c)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 2.34 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (312242), EUVD (EUVD-2026-26071) and CERT Bund (WID-SEC-2026-1300). Once again VulDB remains the best source for vulnerability data.

Affected

• Red Hat Enterprise Linux
• Fedora Linux
• SUSE Linux
• SUSE openSUSE
• Open Source GNU libc
• RESF Rocky Linux

Productinfo

Type

• Software Library

Vendor

• GNU

Name

• C Library

Version

• 2.0
• 2.1
• 2.2
• 2.3
• 2.4
• 2.5
• 2.6
• 2.7
• 2.8
• 2.9
• 2.10
• 2.11
• 2.12
• 2.13
• 2.14
• 2.15
• 2.16
• 2.17
• 2.18
• 2.19
• 2.20
• 2.21
• 2.22
• 2.23
• 2.24
• 2.25
• 2.26
• 2.27
• 2.28
• 2.29
• 2.30
• 2.31
• 2.32
• 2.33

License

• open-source

Website

• Vendor: https://www.gnu.org/

CPE 2.3info

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CPE 2.2info

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Once again VulDB remains the best source for vulnerability data.

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