CyberSecBulletin
CVE-2022-0358NVD status: Modified

QEMU/virtiofsd: Improper Check for Dropped Privileges

Published Updated By the CyberSecBulletin desk

CVE-2022-0358 is a high-severity improper check for dropped privileges vulnerability in QEMU/virtiofsd, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. Affected QEMU/virtiofsd versions: Fixed in qemu v6.2.0-7. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.33% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Qemu to 6.2.0-7 or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
QEMU/virtiofsdQEMU/virtiofsdFixed in qemu v6.2.0-7Not stated
QEMUQemubefore 6.2.0-76.2.0-7
Red HatEnterprise Linux8.0Not stated

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Official description

A flaw was found in the QEMU virtio-fs shared file system daemon (virtiofsd) implementation. This flaw is strictly related to CVE-2018-13405. A local guest user can create files in the directories shared by virtio-fs with unintended group ownership in a scenario where a directory is SGID to a certain group and is writable by a user who is not a member of the group. This could allow a malicious unprivileged user inside the guest to gain access to resources accessible to the root group, potentially escalating their privileges within the guest. A malicious local user in the host might also leverage this unexpected executable file created by the guest to escalate their privileges on the host system.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Check for Dropped Privileges

The product attempts to drop privileges but does not check or incorrectly checks to see if the drop succeeded.

How developers prevent this class of flaw

  • Compartmentalize the system to have safe areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
  • Check the results of all functions that return a value and verify that the value is expected.
  • In Windows, make sure that the process token has the SeImpersonatePrivilege(Microsoft Server 2003). Code that relies on impersonation for security must ensure that the impersonation succeeded, i.e., that a proper privilege demotion happened.

More Improper Check for Dropped Privileges vulnerabilities (CWE-273)

Timeline

  1. CVE record published.
  2. Record last changed materially (score, affected products, status or references).

References

Patches and release notes

Third-party and government advisories

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