CVE-2021-43523: Uclibc

Critical severity, CVSS 9.6. EPSS: 3.1% chance of exploitation in the next 30 days.

In uClibc and uClibc-ng before 1.0.39, incorrect handling of special characters in domain names returned by DNS servers via gethostbyname, getaddrinfo, gethostbyaddr, and getnameinfo can lead to output of wrong hostnames (leading to domain hijacking) or injection into applications (leading to remote code execution, XSS, applications crashes, etc.). In other words, a validation step, which is expected in any stub resolver, does not occur.

Affected products

• Uclibc Uclibc: up to and including 0.9.33.2
• Uclibc-NG Project Uclibc-NG: before 1.0.39 (fixed in 1.0.39)

Published 2021-11-10. Last modified 2026-06-17.