CyberSecBulletin
CVE-2024-53694NVD status: Deferred

QVPN Device Client for Mac: Time-of-check Time-of-use (TOCTOU) Race Condition

Published Updated By the CyberSecBulletin desk

CVE-2024-53694 is a high-severity time-of-check time-of-use (TOCTOU) race condition vulnerability in QVPN Device Client for Mac from QNAP, with a CVSS 4.0 base score of 8.6 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, but only if a user takes part, for example by opening a link or file. The record lists version 2.2.5 as the first without the flaw, so updating QVPN Device Client for Mac to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.13% 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 QVPN Device Client for Mac to 2.2.5 or a later version.
  2. Update Qsync for Mac to 5.1.3 or a later version.
  3. Update Qfinder Pro Mac to 7.11.1 or a later version.
  4. Read the advisory on qnap.com for workarounds and exact fixed builds.
  5. Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.

Affected products and versions

VendorProductAffected versionsFixed in
QNAPQVPN Device Client for Mac2.2.x up to, but not including, 2.2.52.2.5
QNAPQsync for Mac5.1.x up to, but not including, 5.1.35.1.3
QNAPQfinder Pro Mac7.11.x up to, but not including, 7.11.17.11.1

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
LowNo special conditions are needed; the attack works reliably.
Attack requirements
NoneThe attack does not depend on a particular deployment or configuration.
Privileges required
LowA basic user account is enough.
User interaction
ActiveA user must deliberately do something unusual, such as dismissing a warning.
Confidentiality (vulnerable system)
HighSerious loss of confidentiality on the vulnerable system.
Integrity (vulnerable system)
HighSerious loss of integrity on the vulnerable system.
Availability (vulnerable system)
HighSerious loss of availability on the vulnerable system.
Confidentiality (other systems)
HighSerious loss of confidentiality on systems beyond the vulnerable one.
Integrity (other systems)
HighSerious loss of integrity on systems beyond the vulnerable one.
Availability (other systems)
HighSerious loss of availability on systems beyond the vulnerable one.

Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:A/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X. Scored by CNA (qnapsecurity.com.tw).

Official description

A time-of-check time-of-use (TOCTOU) race condition vulnerability has been reported to affect several product versions. If exploited, the vulnerability could allow local attackers who have gained user access to gain access to otherwise unauthorized resources. We have already fixed the vulnerability in the following versions: QVPN Device Client for Mac 2.2.5 and later Qsync for Mac 5.1.3 and later Qfinder Pro Mac 7.11.1 and later

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

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

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