Privilege escalation in Firejail

1) Race condition

EUVDB-ID: #VU50675

Risk: Low

CVSSv3.1: 6.8 [CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-26910

CWE-ID: CWE-367 - Time-of-check Time-of-use (TOCTOU) Race Condition

Exploit availability: No

Description

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to a TOCTOU race condition between a stat operation and an OverlayFS mount operation in firejail. A local user can escalate privileges on the system.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

firejail: 0.9.30 - 0.9.64.2

External links

http://www.openwall.com/lists/oss-security/2021/02/09/1
http://github.com/netblue30/firejail/commit/97d8a03cad19501f017587cc4e47d8418273834b
http://github.com/netblue30/firejail/releases/tag/0.9.64.4
http://lists.debian.org/debian-lts-announce/2021/02/msg00015.html
http://unparalleled.eu/blog/2021/20210208-rigged-race-against-firejail-for-local-root/
http://unparalleled.eu/publications/2021/advisory-unpar-2021-0.txt
http://www.debian.org/security/2021/dsa-4849

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.