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.

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-29373
• https://bugs.chromium.org/p/project-zero/issues/detail?id=2011
• https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.6
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ff002b30181d30cdfbca316dadd099c3ca0d739c