Bug 2024631 (CVE-2021-3995) - CVE-2021-3995 util-linux: Unauthorized unmount of FUSE filesystems belonging to users with similar uid
Summary: CVE-2021-3995 util-linux: Unauthorized unmount of FUSE filesystems belonging ...
Keywords:
Status: CLOSED WONTFIX
Alias: CVE-2021-3995
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 2032274 2044306
Blocks: 2024641
TreeView+ depends on / blocked
 
Reported: 2021-11-18 14:27 UTC by Pedro Sampaio
Modified: 2022-05-17 15:45 UTC (History)
19 users (show)

Fixed In Version: util-linux 2.37.3
Doc Type: If docs needed, set a value
Doc Text:
A logic error was found in the libmount library of util-linux in the function that allows an unprivileged user to unmount a FUSE filesystem. This flaw allows an unprivileged local attacker to unmount FUSE filesystems that belong to certain other users who have a UID that is a prefix of the UID of the attacker in its string form. An attacker may use this flaw to cause a denial of service to applications that use the affected filesystems.
Clone Of:
Environment:
Last Closed: 2022-05-17 15:45:11 UTC
Embargoed:

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Description Pedro Sampaio 2021-11-18 14:27:06 UTC 
A flaw was found in util-linux's libmount. Improper uid check allows an unprivileged user to unmount FUSE filesystems of users with similar uid.
Comment 4 Riccardo Schirone 2021-11-19 16:10:21 UTC 
RHEL 6, 7 and 8 are not affected by this bug as they ship an older version of util-linux which does not allow unprivileged users to unmount FUSE mount points for the current user (e.g. is_fuse_usermount() function does not exist).
Comment 9 Riccardo Schirone 2022-01-24 11:07:14 UTC 
Upstream patch:
https://github.com/util-linux/util-linux/commit/57202f5713afa2af20ffbb6ab5331481d0396f8d
Comment 10 Riccardo Schirone 2022-01-24 11:10:08 UTC 
Release notes:
https://mirrors.edge.kernel.org/pub/linux/utils/util-linux/v2.37/v2.37.3-ReleaseNotes
Comment 11 Riccardo Schirone 2022-01-24 12:01:30 UTC 
Created util-linux tracking bugs for this issue:

Affects: fedora-all [bug 2044306]
Comment 13 Product Security DevOps Team 2022-05-17 15:45:08 UTC 
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-2021-3995
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