Date: Fri, 16 Apr 2021 08:04:50 -0700 From: Steve Beattie <steve.beattie@...onical.com> To: oss-security@...ts.openwall.com Subject: Re: [CVE-2021-3493] Ubuntu Linux kernel overlayfs fs caps privilege escalation On Fri, Apr 16, 2021 at 04:53:50PM +0200, Salvatore Bonaccorso wrote: > Hi Steve, > > On Thu, Apr 15, 2021 at 02:31:14PM -0700, Steve Beattie wrote: > > 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) > > For completeness, this though was in v5.11-rc1 right? Yes, sorry, thanks for the correction. -- Steve Beattie <sbeattie@...ntu.com> Download attachment "signature.asc" of type "application/pgp-signature" (834 bytes)
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