Microsoft Defender Insufficient Granularity of Access Control
CVE-2026-33825 is a high-severity insufficient granularity of access control vulnerability in Microsoft Defender Antimalware Platform 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. The record lists version 4.18.26030.3011 as the first without the flaw, so updating Microsoft Defender Antimalware Platform to that release or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on April 22, 2026, which means attacks have been observed in the wild, including in ransomware campaigns.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update Microsoft Defender Antimalware Platform to 4.18.26030.3011 or a later version.
- Update Defender Antimalware Platform to 4.18.26030.3011 or a later version.
- 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.
- Read the advisory on msrc.microsoft.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Microsoft | Microsoft Defender Antimalware Platform | 4.0.0.0 up to, but not including, 4.18.26030.3011 | 4.18.26030.3011 |
| Microsoft | Defender Antimalware Platform | before 4.18.26030.3011 | 4.18.26030.3011 |
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 CNA (microsoft.com).
Official description
Insufficient granularity of access control in Microsoft Defender allows an authorized attacker to elevate privileges locally.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Insufficient Granularity of Access Control
The product implements access controls via a policy or other feature with the intention to disable or restrict accesses (reads and/or writes) to assets in a system from untrusted agents. However, implemented access controls lack the required granularity
How developers prevent this class of flaw
- Access-control-policy protections must be reviewed for design inconsistency and common weaknesses. Access-control-policy definition and programming flow must be tested in pre-silicon, post-silicon testing.
More Insufficient Granularity of Access Control vulnerabilities (CWE-1220)
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
- Deadline for US federal agencies to remediate, set by CISA.
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-33825US Government Resource
- huntress.com/blog/nightmare-eclipse-intrusionThird Party Advisory
Other vulnerabilities in Microsoft Defender Antimalware Platform
- 7.5 High severity
Microsoft Defender Denial of Service Exploited
Recent Insufficient Granularity of Access Control vulnerabilities
- 9.1 Critical severity
- 8.8 High severity
- 9.1 Critical severity
- 7.5 High severity
- 7.5 High severity
- 8.2 High severity
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