CVE-2025-55248: .NET Framework Info Disclosure Flaw

CVE-2025-55248 Overview

CVE-2025-55248 is an information disclosure vulnerability affecting Microsoft .NET, .NET Framework, and Visual Studio. The flaw stems from inadequate encryption strength [CWE-326] in cryptographic operations performed by these components. An authorized attacker with low privileges can disclose sensitive information transmitted over a network when a user is induced to interact with crafted content.

The vulnerability is tracked across multiple Microsoft platforms, including .NET Framework versions 3.0 through 4.8.1, modern .NET, and Visual Studio 2022. Both server and client Windows editions are affected, alongside cross-platform .NET runtimes on macOS and Linux.

Critical Impact

Attackers leveraging weak cryptographic protections can intercept or decrypt protected network traffic and disclose confidential information processed by .NET applications.

Affected Products

• Microsoft .NET Framework 3.0 SP2, 3.5, 3.5.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
• Microsoft .NET (cross-platform on Windows, macOS, and Linux)
• Microsoft Visual Studio 2022

Discovery Timeline

• 2025-10-14 - CVE-2025-55248 published to NVD
• 2025-10-14 - Microsoft releases security advisory and patches
• 2025-10-23 - Last updated in NVD database

Technical Details for CVE-2025-55248

Vulnerability Analysis

The vulnerability falls under [CWE-326] Inadequate Encryption Strength. Microsoft .NET, .NET Framework, and Visual Studio implement cryptographic routines that do not provide sufficient protection against network-level attackers. The weakness allows an authorized adversary to disclose information processed by affected applications.

Exploitation requires the attacker to hold valid low-privilege access and requires user interaction with attacker-controlled content. The scope of the impact is confidentiality only; integrity and availability are not directly affected. Because the cryptographic weakness sits inside framework-level libraries, any managed application relying on the affected APIs inherits the exposure.

The attack is performed over the network, which means an attacker positioned to observe or manipulate communications between the victim and an attacker-controlled endpoint can recover protected data. This class of weakness typically manifests as use of short keys, deprecated algorithms, predictable IVs, or insufficient entropy in protocol implementations.

Root Cause

The root cause is the use of cryptographic primitives or parameters that fall below current strength requirements within the .NET cryptographic stack. When affected APIs are used to protect data sent across a network, the resulting ciphertext is recoverable by an attacker with the right vantage point and access level.

Attack Vector

An attacker authenticates to an environment that processes data through a vulnerable .NET runtime or Visual Studio component. The attacker then induces a target user to interact with crafted content, such as a malicious document or link that triggers network communication. By observing the resulting traffic, the attacker recovers sensitive plaintext from inadequately protected ciphertext.

No proof-of-concept code is published. Microsoft has not reported observed exploitation, and the issue is not listed on the CISA Known Exploited Vulnerabilities catalog. Refer to the Microsoft Security Advisory CVE-2025-55248 for technical details.

Detection Methods for CVE-2025-55248

Indicators of Compromise

• Unexpected outbound network connections from dotnet.exe, w3wp.exe, or other managed processes to untrusted hosts following user interaction with external content.
• Presence of unpatched mscorlib.dll, System.Security.Cryptography.* assemblies, or older .NET Framework builds on systems handling sensitive data.

Detection Strategies

• Inventory installed .NET Framework, .NET runtime, and Visual Studio 2022 versions, then flag any below the October 2025 security baseline.
• Inspect TLS and cryptographic configurations in .NET applications for use of weak algorithms or short key lengths that could be downgraded.
• Correlate user interaction events (document opens, link clicks) with subsequent network traffic from .NET-hosted processes for anomaly review.

Monitoring Recommendations

• Enable network telemetry that captures cipher suite negotiation for traffic originating from .NET applications.
• Alert on installation or execution of legacy .NET Framework versions on hosts that process regulated data.
• Audit Visual Studio 2022 build hosts for unpatched runtimes used to compile or test cryptographic code.

How to Mitigate CVE-2025-55248

Immediate Actions Required

• Apply the October 2025 Microsoft security updates listed in the Microsoft Security Advisory CVE-2025-55248 to all affected systems.
• Update Visual Studio 2022 to the latest servicing release on developer and build machines.
• Restrict low-privileged user accounts from executing arbitrary external content or links delivered through email and web channels.

Patch Information

Microsoft published patches for .NET, .NET Framework, and Visual Studio 2022 on 2025-10-14. Updates are delivered through Windows Update, Microsoft Update Catalog, and Visual Studio Installer. Apply the cumulative update appropriate for each supported .NET Framework branch (3.5, 4.6.2, 4.7.x, 4.8, 4.8.1) and modern .NET runtime.

Workarounds

• Configure affected applications to enforce TLS 1.2 or higher with strong cipher suites until patches are deployed.
• Disable or remove legacy .NET Framework 3.5 from systems where it is not required.
• Limit user interaction with untrusted documents and links through application allowlisting and email filtering policies.