Bugzilla – Bug 1184900
VUL-1: CVE-2021-3493: kernel-source: overlayfs fs caps privilege escalation
Last modified: 2021-04-20 14:35:34 UTC
CVE-2021-3493 oss-sec mailing list archives By Date By Thread [CVE-2021-3493] Ubuntu Linux kernel overlayfs fs caps privilege escalation From: Steve Beattie Date: Thu, 15 Apr 2021 14:31:14 -0700 Hello, An independent security researcher reported via the SSD Secure Disclosure program that the overlayfs stacking file system within the Linux kernel as used within Ubuntu did not properly validate the application of file capabilities against user namespaces. This issue is likely Ubuntu specific, as Ubuntu carries a patch to enable unprivileged overlayfs mounts. The combination of that patch plus allowing unprivileged user namespaces by default in Ubuntu allows an unprivileged attacker to gain elevated privileges. A commit that addresses the issue was applied in the upstream kernel: 7c03e2cda4a5 ("vfs: move cap_convert_nscap() call into vfs_setxattr()") (v5.10) https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a5 It was added prior to the upstream kernel commit allowing unprivileged overlayfs mounts: 459c7c565ac3 ("ovl: unprivieged mounts") (v5.11) https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=459c7c565ac3 Thus the upstream Linux kernel is not affected. -- Steve Beattie Attachment: signature.asc Description: By Date By Thread Current thread: [CVE-2021-3493] Ubuntu Linux kernel overlayfs fs caps privilege escalation Steve Beattie (Apr 16) References: http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2021-3493 http://seclists.org/oss-sec/2021/q2/24
I think we're okay here. We don't carry overlayfs unprivileged mount support (FS_USERNS_MOUNT) in any SLE branches.
Ok, thx. Bouncing back.
Closing as invalid.