GNU C Library on Linux: which version fixes what

What it is, and why it is on your server

The GNU C Library provides the basic system interfaces every program uses, from memory allocation to name resolution. It is packaged as libc6 on Debian and Ubuntu and glibc on Rocky and AlmaLinux.

Why its advisories behave the way they do

• The reachable-from-anywhere flaws are the dangerous ones. The name resolution and printf paths are reached by code that never intended to handle untrusted input, which is what made Looney Tunables and the 2015 getaddrinfo bug so serious.
• A restart list is not enough. So many processes link glibc that the practical answer after patching is a reboot, and a server that has not rebooted since the patch is still running the old library.
• It is the package administrators most fear touching. A botched glibc upgrade can leave a machine unable to run anything, and that fear is why unpatched glibc lingers longer than almost anything else.

Check what you are actually running

The version that matters is the package version, not the upstream one. Distributions backport security fixes without changing the number before the dash, so a release that looks years old is frequently fully patched, and the revision after the dash is the only part that tells you.

dpkg-query -W -f='${Package} ${Version}\n' libc6 libc-bin 2>/dev/null

rpm -q glibc glibc-common

Check how long it has been since the machine last rebooted with `uptime -s`. If that is older than the glibc package, the fix is on disk and not in memory.

Fixed versions, per distribution

Each distribution patches on its own schedule and under its own version scheme, so the same CVE has a different answer on each of them. These come from the distributions’ own advisory data, asked per release. Where a release has no fixed version, that is what the advisory says, not a gap in the data.

Advisory data last refreshed 28 October 2026. It is re-read daily.

What this page does not tell you

It does not tell you whether your server is affected. A CVE applying to a package is not the same as a CVE applying to your installation: the fix may already be backported into what you are running, the vulnerable module may not be loaded, or the service may not be reachable from anywhere that matters. Answering that needs the versions on your machine, not a list.

It also carries no count of how many servers are affected. SecAI monitors a small fleet, and a percentage drawn from it would be arithmetic on a sample too small to mean anything. When that changes, the number will appear here and the page will say when it started.

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