An issue was discovered in fs/io_uring.c in the Linux kernel before 5.6. It unsafely handles the root directory during path lookups, and thus a process inside a mount namespace can escape to unintended filesystem locations, aka CID-ff002b30181d.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ff002b30181d30cdfbca316dadd099c3ca0d739c
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.6
Source: Mitre, NVD
Published: 2020-11-28
Updated: 2020-12-02
Base Score: 2.1
Vector: CVSS2#AV:L/AC:L/Au:N/C:P/I:N/A:N
Severity: Low
Base Score: 6.5
Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
Severity: Medium