Bug 2463539 (CVE-2026-6238)

Summary: CVE-2026-6238 glibc: glibc: Application crash or uninitialized memory read via crafted DNS response
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: ashankar, codonell, dj, fweimer, pfrankli, rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in glibc (GNU C Library). The deprecated functions ns_printrrf, ns_printrr, and fp_nquery do not properly validate the length of RDATA (Resource Record Data) in a DNS (Domain Name System) response when processing specific record types like LOC, CERT, TKEY, or TSIG. A remote attacker could craft a malicious DNS response, leading to a target application crashing or reading uninitialized memory. These functions are intended for application debugging and are not part of the standard DNS resolver path.
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Description OSIDB Bzimport 2026-04-28 19:09:53 UTC
The deprecated functions ns_printrrf, ns_printrr and fp_nquery in the GNU C Library version 2.2 and newer fail to validate the RDATA content against the RDATA length in a DNS response when processing LOC, CERT, 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.