Ask Klaus
Ask Klaus
Klaus Knopper answers your Linux questions.
DNS Security Bug
What's the easiest way to get rid of the dangerous "DNS resolver" security bug that was recently detected (CVE-2015-7547)? Security lists tell me that all programs that resolve Internet names to IP addresses are affected, such as Firefox, LibreOffice, and various KDE and Gnome programs. Do I have to upgrade all of them?
It is the GLIBC implementation of the C libraries getaddrinfo() function that causes a stack overflow in case of specially crafted answers from a direct name server query. Programs can crash or execute arbitrary code due to this bug, but in order to exploit it, the attacker must first manipulate a DNS server that's queried by your client system. If your Linux system is behind an access point or router that acts as a DNS proxy, chances are that you are safe, because the DNS proxy may already replace bad replies by an "address not available" response. However, you should upgrade as soon as possible anyway – not the entire system, but definitely the glibc libraries that contain the vulnerability.
For Debian-based systems, updating the libc6 package is sufficient to fix all programs dynamically linked with libc6; these are the commands for Knoppix/Debian:
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