CyberSecBulletin
CVE-2023-27327NVD status: Analyzed

Desktop: Time-of-check Time-of-use (TOCTOU) Race Condition

Published Updated By the CyberSecBulletin desk

CVE-2023-27327 is a high-severity time-of-check time-of-use (TOCTOU) race condition vulnerability in Desktop from Parallels, with a CVSS 3.0 base score of 7.5 out of 10. It can be exploited with local access to the system by an attacker with administrator privileges, without any action from a user. Affected Desktop versions: 18.0.2. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.4% 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 parallels_desktop to 18.1.1 or a later version.
  2. Read the advisory on kb.parallels.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
ParallelsDesktop18.0.2Not stated
Parallelsparallels_desktopbefore 18.1.118.1.1

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
HighSuccess depends on conditions outside the attacker's control.
Privileges required
HighAdministrator-level access is required first.
User interaction
NoneNo action by a victim is required.
Scope
ChangedThe attack can reach beyond the vulnerable component into other systems.
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:3.0/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H. Scored by CNA (trendmicro.com).

Official description

Parallels Desktop Toolgate Time-Of-Check Time-Of-Use Local Privilege Escalation Vulnerability. This vulnerability allows local attackers to escalate privileges on affected installations of Parallels Desktop. An attacker must first obtain the ability to execute high-privileged code on the target guest system in order to exploit this vulnerability. The specific flaw exists within the Toolgate component. The issue results from the lack of proper locking when performing operations on an object. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of the current user on the host system. Was ZDI-CAN-18964.

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

The underlying weakness: Time-of-check Time-of-use (TOCTOU) Race Condition

The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.

How developers prevent this class of flaw

  • The most basic advice for TOCTOU vulnerabilities is to not perform a check before the use. This does not resolve the underlying issue of the execution of a function on a resource whose state and identity cannot be assured, but it does help to limit the false sense of security given by the check.
  • When the file being altered is owned by the current user and group, set the effective gid and uid to that of the current user and group when executing this statement.
  • Limit the interleaving of operations on files from multiple processes.

More Time-of-check Time-of-use (TOCTOU) Race Condition vulnerabilities (CWE-367)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Third-party and government advisories

Other vulnerabilities in Desktop

All Desktop vulnerabilities

Recent Time-of-check Time-of-use (TOCTOU) Race Condition vulnerabilities

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