CVE-2021-21284: Debian Linux

Medium severity, CVSS 6.8. EPSS: 1.1% chance of exploitation in the next 30 days.

In Docker before versions 9.03.15, 20.10.3 there is a vulnerability involving the --userns-remap option in which access to remapped root allows privilege escalation to real root. When using "--userns-remap", if the root user in the remapped namespace has access to the host filesystem they can modify files under "/var/lib/docker/<remapping>" that cause writing files with extended privileges. Versions 20.10.3 and 19.03.15 contain patches that prevent privilege escalation from remapped user.

Affected products

• Debian Debian Linux: version 10.0 only
• Docker Docker: before 19.03.15 (fixed in 19.03.15); from 20.0.0, before 20.10.3 (fixed in 20.10.3)
• Netapp E-Series Santricity OS Controller: from 11.0.0, up to and including 11.60.3

Published 2021-02-02. Last modified 2026-06-17.