How to check if a Debian update is available

Sometimes we need to patch packages on OS distributions which are close or past EOL.

If upstream updates are still available, it saves us a lot of effort patching dependencies from binary.

To verify if an upstream update is available (e.g. curl), you can search in the security-tracker website like below:

Information on source package curl

On my recent search, Debian Buster should receive a u7 update:

buster (security)7.64.0–4+deb10u7

In my environment, I could only patch to u6.

# apt-cache policy curl
curl:
  Installed: 7.64.0-4+deb10u6
  Candidate: 7.64.0-4+deb10u6

A simple fix is to run apt update , then the new update candidate will be shown:

# apt-cache policy curl
curl:
  Installed: 7.64.0-4+deb10u6
  Candidate: 7.64.0-4+deb10u7