CyberSecBulletin
CVE-2018-8639Exploited in the wildNVD status: Analyzed

Microsoft Windows Win32k Improper Resource Shutdown or Release

Published Updated By the CyberSecBulletin desk

CVE-2018-8639 is a high-severity improper resource shutdown or release vulnerability in Windows 7 from Microsoft, 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 Windows 7 versions: 32-bit Systems Service Pack 1; x64-based Systems Service Pack 1. The record does not name a fixed version, so check the vendor advisory. CISA added it to the Known Exploited Vulnerabilities catalogue on March 3, 2025, which means attacks have been observed in the wild, including in ransomware campaigns.

Patch now

Attackers are already exploiting this vulnerability, according to CISA.

What to do

  1. Check which version of Windows 7 you run against the affected versions below, and install the vendor's latest release.
  2. CISA's required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
  3. Read the advisory on portal.msrc.microsoft.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
MicrosoftWindows 732-bit Systems Service Pack 1; x64-based Systems Service Pack 1Not stated
MicrosoftWindows Server 2012 R2(Server Core installation)Not stated
MicrosoftWindows RT 8.1Windows RT 8.1Not stated
MicrosoftWindows Server 200832-bit Systems Service Pack 2; 32-bit Systems Service Pack 2 (Server Core installation); Itanium-Based Systems Service Pack 2; x64-based Systems Service Pack 2; x64-based Systems Service Pack 2 (Server Core installation)Not stated
MicrosoftWindows Server 2019(Server Core installation)Not stated
MicrosoftWindows Server 2012(Server Core installation)Not stated
MicrosoftWindows 8.132-bit systems; x64-based systemsNot stated
MicrosoftWindows Server 2016(Server Core installation)Not stated
MicrosoftWindows Server 2008 R2Itanium-Based Systems Service Pack 1; x64-based Systems Service Pack 1; x64-based Systems Service Pack 1 (Server Core installation)Not stated
MicrosoftWindows 1032-bit Systems; Version 1607 for 32-bit Systems; Version 1607 for x64-based Systems; Version 1703 for 32-bit Systems; Version 1703 for x64-based Systems; Version 1709 for 32-bit Systems; Version 1709 for ARM64-based Systems; Version 1709 for x64-based Systems; and 7 more rangesNot stated
MicrosoftWindows 10 Serversversion 1709 (Server Core Installation); version 1803 (Server Core Installation)Not stated
MicrosoftWindows 10 1507Not specified in the recordNot stated
MicrosoftWindows 10 1607Not specified in the recordNot stated
MicrosoftWindows 10 1703Not specified in the recordNot stated
MicrosoftWindows 10 1709Not specified in the recordNot stated
MicrosoftWindows 10 1803Not specified in the recordNot stated
MicrosoftWindows 10 1809Not specified in the recordNot 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.

Scoring systemScoreSeverityScored by
CVSS 3.17.8HighNVD
CVSS 3.18.4HighCISA (ADP)
CVSS 2.07.2HighNVD

Official description

An elevation of privilege vulnerability exists in Windows when the Win32k component fails to properly handle objects in memory, aka "Win32k Elevation of Privilege Vulnerability." This affects Windows 7, Windows Server 2012 R2, Windows RT 8.1, Windows Server 2008, Windows Server 2019, Windows Server 2012, Windows 8.1, Windows Server 2016, Windows Server 2008 R2, Windows 10, Windows 10 Servers. This CVE ID is unique from CVE-2018-8641.

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

The underlying weakness: Improper Resource Shutdown or Release

The product does not release or incorrectly releases a resource before it is made available for re-use.

How developers prevent this class of flaw

  • Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, languages such as Java, Ruby, and Lisp perform automatic garbage collection that releases memory for objects that have been deallocated.
  • It is good practice to be responsible for freeing all resources you allocate and to be consistent with how and where you free memory in a function. If you allocate memory that you intend to free upon completion of the function, you must be sure to free the memory at all exit points for that function including error conditions.
  • Memory should be allocated/freed using matching functions such as malloc/free, new/delete, and new[]/delete[].

More Improper Resource Shutdown or Release vulnerabilities (CWE-404)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
  3. Added to CISA's Known Exploited Vulnerabilities catalogue.
  4. Deadline for US federal agencies to remediate, set by CISA.
  5. Record last changed materially (score, affected products, status or references).

References

Third-party and government advisories

Recent Improper Resource Shutdown or Release vulnerabilities

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