The bubblewrap sandbox of WebKitGTK and WPE WebKit, prior to 2.28.3, failed to properly block access to CLONE_NEWUSER and the TIOCSTI ioctl. CLONE_NEWUSER could potentially be used to confuse xdg-desktop-portal, which allows access outside the sandbox. TIOCSTI can be used to directly execute commands outside the sandbox by writing to the controlling terminal's input buffer, similar to CVE-2017-5226.
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00074.html
https://security.gentoo.org/glsa/202007-11
https://trac.webkit.org/changeset/262368/webkit
https://usn.ubuntu.com/4422-1/
Source: MITRE
Published: 2020-07-14
Updated: 2020-07-27
Type: CWE-20
Base Score: 7.5
Vector: AV:N/AC:L/Au:N/C:P/I:P/A:P
Impact Score: 6.4
Exploitability Score: 10
Severity: HIGH
Base Score: 10
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Impact Score: 6
Exploitability Score: 3.9
Severity: CRITICAL