CyberSecBulletin
CVE-2022-33905NVD status: Modified

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

Published Updated By the CyberSecBulletin desk

CVE-2022-33905 is a high-severity time-of-check time-of-use (TOCTOU) race condition vulnerability in Kernel from Insyde, with a CVSS 3.1 base score of 7.0 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. The record lists versions 5.2.05.27.23, 5.3.05.36.23, 5.4.05.44.23 as the first without the flaw, so updating Kernel to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.14% 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 Kernel to 5.2.05.27.23 or 5.3.05.36.23 or 5.4.05.44.23 or 5.5.05.52.23, whichever matches your release line, or a later version.
  2. Read the advisory on insyde.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
InsydeKernel5.2 up to, but not including, 5.2.05.27.23; 5.3 up to, but not including, 5.3.05.36.23; 5.4 up to, but not including, 5.4.05.44.23; 5.5 up to, but not including, 5.5.05.52.235.2.05.27.23, 5.3.05.36.23, 5.4.05.44.23, 5.5.05.52.23

Version data comes from NVD's product matching. 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
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:H/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.17.0HighNVD
CVSS 3.17.0HighCISA (ADP)

Official description

DMA transactions which are targeted at input buffers used for the AhciBusDxe software SMI handler could cause SMRAM corruption (a TOCTOU attack). DMA transactions which are targeted at input buffers used for the software SMI handler used by the AhciBusDxe driver could cause SMRAM corruption through a TOCTOU attack. This issue was discovered by Insyde engineering based on the general description provided by Intel's iSTARE group, Fixed in kernel 5.2: 05.27.23, kernel 5.3: 05.36.23, kernel 5.4: 05.44.23, kernel 5.5: 05.52.23 https://www.insyde.com/security-pledge/SA-2022047

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: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in Kernel

All Kernel vulnerabilities

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

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