CVE-2026-8674

Description

Initializing the DNS stub resolver from an /etc/resolv.conf file, or a LOCALDOMAIN environment variable, whose search list contains a domain of roughly 200 characters or more in the GNU C Library version 2.26 to 2.44 results in an assertion failure which aborts the process. The resolver truncates the search list when copying it into the fixed-size _res.defdname buffer, then asserts that the copy is consistent with the full configuration. The consistency check compared against the wrong size and did not handle a first entry that does not fit, so a correctly truncated list failed the assertion. Any process that resolves names through the library is affected, including long-running processes that reload /etc/resolv.conf on the next query after it changes. Search domains are commonly written to /etc/resolv.conf from data received over DHCP or from a VPN server, so an attacker on the local network may be able to trigger this without privileges on the target system, subject to validation by the network configuration software.

References

• https://joshua.hu/fuzzing-glibc-libresolv
• https://sourceware.org/bugzilla/show_bug.cgi?id=31026
• https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=advisories/GLIBC-SA-2026-0021
• https://sourceware.org/git/?p=glibc.git;a=commit;h=506ea57086bfb9ce3daff1c14246a1cb532aba0a
• http://www.openwall.com/lists/oss-security/2026/09/17/4