ArchLinux: 202105-17: runc: sandbox escape
Summary
runc 1.0.0-rc94 and earlier are vulnerable to a symlink exchange attack where an attacker with the ability to start containers using a custom volume configuration can request a seemingly-innocuous container configuration that results in the host filesystem being bind-mounted into the container (allowing for a container escape).
Resolution
Upgrade to 1.0.0rc95-1.
# pacman -Syu "runc>=1.0.0rc95-1"
The problem has been fixed upstream in version 1.0.0rc95.
References
https://github.com/opencontainers/runc/security/advisories/GHSA-c3xm-pvg7-gh7r https://github.com/opencontainers/runc/commit/0ca91f44f1664da834bc61115a849b56d22f595f https://security.archlinux.org/CVE-2021-30465
Workaround
Container hardening mechanisms such as LSMs (AppArmor/SELinux) and usernamespaces can restrict the amount of damage an attacker could do butthey do not block this attack outright.