CVE-2021-3996
Published: 23 August 2022
Summary
CVE-2021-3996 is a medium-severity Files or Directories Accessible to External Parties (CWE-552) vulnerability in Kernel Util-Linux. Its CVSS base score is 5.5 (Medium).
Operationally, ranked at the 38.2th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2021-27186
Vulnerability details
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 a local user on a vulnerable system to unmount other users' filesystems that…
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are either world-writable themselves (like /tmp) or mounted in a world-writable directory. An attacker may use this flaw to cause a denial of service to applications that use the affected filesystems.
- CWE(s)
Related Threats
No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.
Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Controls on authorized publication limit files and directories with nonpublic data from becoming accessible to external parties.
Controlling and documenting P2P file sharing prevents files and directories from being made accessible to external parties for unauthorized distribution.
Identifying and documenting file and directory locations allows restriction of access to external parties.
Protecting backup files ensures they are not accessible to external parties or unauthorized spheres.
Sanitizing equipment before off-site maintenance reduces the risk of files or directories containing sensitive data becoming accessible to external parties.
Policy restricts media access to authorized parties only, preventing exposure of resources to external or unauthorized actors.
Media access restrictions prevent files or directories from being accessible to external parties.
Employing and evaluating controls at documented alternate sites makes files and directories less likely to be accessible to external parties through physical or environmental weaknesses.