CVE-2026-6238

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.

Red Hat has rated this glibc flaw as having MODERATE impact (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H, score 6.5). The deprecated functions ns_printrrf(), ns_printrr(), and fp_nquery() in the GNU C Library fail to validate the RDATA content against the RDATA length of a DNS response when processing LOC, CERT, TKEY, or TSIG records. A remote attacker who can supply a crafted DNS response to an application that uses these functions could cause that application to crash or read uninitialized memory. Exposure is limited because these functions are intended for application debugging only, are not part of the code path executed by the DNS resolver, and have been deprecated since glibc 2.34. Within the Red Hat portfolio, the glibc packages shipped in Red Hat Enterprise Linux 8.10, 9.8, and 10.2, and in the Red Hat Hardened Images (hummingbird-1) product were affected, and fixes for these delegated components have been delivered through their respective product updates. Other Red Hat Enterprise Linux streams, the OpenShift Container Platform RHCOS images, and Fedora were assessed as not affected because the vulnerable code is not present in the glibc packages shipped in those products.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

The affected functions are deprecated, application-debugging-only interfaces that are not part of the DNS resolver code path. Applications that call ns_printrrf(), ns_printrr(), or fp_nquery() can mitigate this issue by porting away from these interfaces, as recommended upstream, since they are not required for DNS resolution. For applications that cannot be changed, update to the glibc packages containing the fix that were released for the affected Red Hat products.