Microsoft .NET Type Confusion Vulnerability Allows Remote Privilege Escalation
Microsoft confirms a high-severity type confusion vulnerability in .NET that allows unauthorized network attackers to elevate privileges.
Key points
- CVE-2026-102869 carries a CVSS score of 8.8, classified as high severity.
- The flaw affects multiple versions of the .NET Framework.
- Attackers can exploit the issue remotely to gain elevated privileges.
Microsoft has disclosed a significant security flaw in its .NET Framework products. The vulnerability, tracked as CVE-2026-102869, allows an unauthorized attacker to elevate privileges over a network connection. According to the National Vulnerability Database, the issue stems from a type confusion error, where resources are accessed using incompatible data types. This misclassification enables the attacker to bypass normal security boundaries and gain higher-level access rights on the affected system. The flaw is rated high severity with a CVSS score of 8.8.
How it unfolded
- Microsoft published an advisory detailing the elevation of privilege vulnerability in .NET.
- The National Vulnerability Database recorded the flaw with a CVSS score of 8.8 and linked it to CWE-843.
- Affected product versions were identified, ranging from .NET Framework 3.5 to 4.8.1, prior to specific build numbers.
Who is affected
The vulnerability impacts a wide range of Microsoft .NET Framework versions. Affected software includes .NET Framework 3.5 combined with versions 4.6.2 through 4.7.2, provided they are before build 2.0.50727.8987 or 4.7.4150.0. .NET Framework 4.8 is vulnerable if it precedes build 4.8.4811.0, while .NET Framework 4.8.1 is at risk before build 4.8.9363.0. Systems running these specific older builds are exposed to this remote attack vector.
The fix
No fix has been confirmed yet. The source material lists vulnerable versions and their corresponding safe build numbers but does not explicitly state that a patch or update has been released. Organizations should monitor official channels for further guidance. Until a confirmed update is available, systems running the affected versions remain vulnerable to remote exploitation of this type confusion flaw.
What made it possible
Type confusion occurs when software misinterprets the data type of an object, leading to incorrect memory handling. In intrusion scenarios, attackers exploit this mismatch to execute unauthorized operations or escalate privileges. Security teams usually monitor for anomalous behavior in managed code environments, such as unexpected access patterns or crashes. Check whether applications validate input types strictly before processing. Understanding how type mismatches can bypass security controls helps in identifying similar weaknesses in legacy systems that rely on older framework versions.
What to do and how to stay safe: Microsoft
- Audit all servers and workstations to identify installations of vulnerable .NET Framework versions.
- Monitor network traffic for unusual connection attempts that could indicate exploitation attempts.
- Review access logs for signs of privilege escalation on systems that cannot be immediately patched.
- Wait for the vendor to provide an update before attempting unverified mitigation steps.
Step-by-step guide: What Is Virtual Patching: How It Works Without Code Changes
General security guidance from the RedTeam Tribune newsroom. It is not confirmed advice from the organisations named in this story.
Frequently asked questions
What is the CVSS score for CVE-2026-102869?
The National Vulnerability Database rates the vulnerability at 8.8, which is classified as high severity.
Which .NET Framework versions are affected?
Versions 3.5, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, and 4.8.1 are affected if they are below the specified safe build numbers.
Can this vulnerability be exploited remotely?
Yes, the advisory states that an unauthorized attacker can elevate privileges over a network connection.
