Windows: Unprotected Alternate Channel
CVE-2025-59033 is a high-severity unprotected alternate channel vulnerability in Windows from Microsoft, with a CVSS 3.1 base score of 7.4 out of 10. It can be exploited with local access to the system by an unauthenticated attacker, without any action from a user. Affected Windows versions: 10 through Server 2025. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.3% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of Windows you run against the affected versions below, and install the vendor's latest release.
Affected products and versions
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
- NoneNo account or login is needed.
- 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:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (mitre.org).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.4 | High | CNA (mitre.org) |
| CVSS 3.1 | 6.7 | Medium | CISA (ADP) |
Official description
The Microsoft vulnerable driver block list is implemented as Windows Defender Application Control (WDAC) policy. Entries that specify only the to-be-signed (TBS) part of the code signer certificate are properly blocked, but entries that specify the signing certificate's TBS hash along with a 'FileAttribRef' qualifier (such as file name or version) may not be blocked, whether hypervisor-protected code integrity (HVCI) is enabled or not. NOTE: The vendor disputes this CVE ID assignment and states that the driver blocklist is intended for use with HVCI.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Unprotected Alternate Channel
The product protects a primary channel, but it does not use the same level of protection for an alternate channel.
How developers prevent this class of flaw
- Identify all alternate channels and use the same protection mechanisms that are used for the primary channels.
More Unprotected Alternate Channel vulnerabilities (CWE-420)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
Other vulnerabilities in Windows
- 7.4 High severity
- 7.8 High severity
- 7.5 High severity
- 7.0 High severity
- 7.8 High severity
- 7.8 High severity
Recent Unprotected Alternate Channel vulnerabilities
- 9.8 Critical severity
CrushFTP Unprotected Alternate Channel Exploited
- 9.9 Critical severity
- 7.8 High severity
- 8.1 High severity
- 8.1 High severity
- 7.3 High severity
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