An attacker with a low-privileged user on a Linux machine with an overlay mount can escalate his privileges up to root when performing rename in specific way with this overlayfs. Reference: a295aef603e1 ("ovl: fix missing negative dentry check in ovl_rename()")
This issue has been addressed in the following products: Red Hat Enterprise Linux 8 Via RHSA-2021:5241 https://access.redhat.com/errata/RHSA-2021:5241
This issue has been addressed in the following products: Red Hat Enterprise Linux 8 Via RHSA-2021:5227 https://access.redhat.com/errata/RHSA-2021:5227
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s): https://access.redhat.com/security/cve/cve-2021-20321