The GNU C Library security advisory update for 2026-09-10

glibc advisory GLIBC-SA-2026-0016: nscd can crash from a stack overflow when an untrusted DNS server returns oversized responses.

A new GNU C Library advisory (GLIBC-SA-2026-0016) describes a stack overflow in the nscd service caused by unbounded alloca use. glibc 2.3.4 and newer may crash when a malicious DNS server returns an oversized response, resulting in degraded DNS resolution. Exploitation requires nscd to be enabled and the system to be using an untrusted DNS server. The advisory was posted to oss-security by glibc maintainer Siddhesh Poyarekar.

• nscd in glibc 2.3.4 and newer can crash via unbounded alloca stack overflow
• Triggered by a malicious DNS server returning too-large responses to DNS queries
• Impact is degraded DNS resolution; requires nscd enabled with untrusted DNS
• Published as GLIBC-SA-2026-0016 in the glibc security advisory update