Privilege escalation in Linux Kernel

1) Privilege escalation

EUVDB-ID: #VU15836

Risk: Low

CVSSv3.1: 7.2 [CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C]

CVE-ID: CVE-2018-18955

CWE-ID: CWE-264 - Permissions, Privileges, and Access Controls

Exploit availability: Yes

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.

Mitigation

The vulnerability has been fixed in the versions 4.18.19, 4.19.2.

Vulnerable software versions

Linux kernel: 4.0 - 4.19.1

External links

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

Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, a fully functional exploit for this vulnerability is available.