Privilege escalation in Linux kernel - CVE-2018-18955

Detailed vulnerability description

The vulnerability allows a local attacker to gain elevated privileges on a targeted system.

The weakness exists due to the map_write() function, as defined in the kernel/user_namespace.c source code file, improperly handles nested user namespaces that have more than five user identifier (UID) or group identifier (GID) ranges. A local attacker with CAP_SYS_ADMIN capabilities in a targeted user namespace can access the system and execute an application that submits malicious input to bypass access controls outside the user namespace and gain elevated privileges on the system.

How to mitigate CVE-2018-18955

Sources

• https://github.com/torvalds/linux/commit/d2f007dbe7e4c9583eea6eb04d60001e85c6f1bd
• https://www.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.19.2
• https://www.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.20