#VU18375 Race condition in Snapd - CVE-2019-11503

Vulnerability identifier: #VU18375

Vulnerability risk: Low

CVSSv4.0: 1.9 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P/U:Clear]

CVE-ID: CVE-2019-11503

CWE-ID: CWE-362

Exploitation vector: Local

Exploit availability: No

Vulnerable software:
Snapd
Universal components / Libraries / Software for developers

Vendor: snapcore

Description

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

The vulnerability exists due to a race condition when processing symlinks using the chdir() function to restore a working directory. A local user can run snap-confine on a specially crafted symlink and restore files without necessary permissions. 

Mitigation
Install update from vendor's website.

Vulnerable software versions

Snapd: 2.0 - 2.38.1

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External links
https://www.openwall.com/lists/oss-security/2019/04/25/7
https://github.com/snapcore/snapd/pull/6642
https://www.openwall.com/lists/oss-security/2019/04/18/4

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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, proof of concept for this vulnerability is available.