CVE-2026-62900: .NET Information Disclosure Vulnerability

CVE-2026-62900 Overview

CVE-2026-62900 is an information disclosure vulnerability in Microsoft .NET. The flaw stems from improper removal of sensitive information before storage or transfer [CWE-212]. An unauthenticated attacker can exploit this weakness over a network to disclose sensitive data processed by affected .NET components.

The vulnerability requires no privileges and no user interaction, but exploitation carries high attack complexity. Confidentiality is impacted while integrity and availability remain intact. Microsoft published guidance through its Security Update Guide.

Critical Impact
An unauthorized remote attacker can disclose sensitive information transferred or stored by .NET applications without any authentication or user interaction.

Affected Products

Microsoft .NET (specific versions listed in the Microsoft Security Update Guide)
Applications and services built on affected .NET runtimes
Workloads processing sensitive data through vulnerable .NET components

Discovery Timeline

2026-08-11 - CVE-2026-62900 published to NVD
2026-08-11 - Last updated in NVD database

Technical Details for CVE-2026-62900

Vulnerability Analysis

The vulnerability is classified under [CWE-212]: Improper Removal of Sensitive Information Before Storage or Transfer. Affected .NET code paths retain sensitive information in data that gets stored or transmitted over a network. An attacker positioned to observe the resulting data can extract confidential content that should have been scrubbed.

This class of flaw typically arises when serialization, logging, error handling, or caching routines fail to strip credentials, tokens, or internal state before the data leaves a trust boundary. The confidentiality impact is high, while integrity and availability are not affected.

Exploitation over a network is possible without authentication or user interaction. The high attack complexity reflects specific conditions the attacker must meet, such as observing particular traffic patterns or triggering code paths that emit residual sensitive data.

Root Cause

The root cause is incomplete sanitization inside affected .NET routines. Sensitive fields persist in objects, buffers, or transport payloads after a sanitization step should have removed them. Microsoft's advisory identifies the affected components and corrected behavior.

Attack Vector

The attack vector is network-based. An attacker interacts with a service running vulnerable .NET code, or observes network output the service produces, to recover sensitive information. No credentials or victim interaction are required.

No public proof-of-concept exploit is available at this time, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. Refer to the Microsoft Security Update Guide entry for authoritative technical details.

Detection Methods for CVE-2026-62900

Indicators of Compromise

Outbound responses from .NET services containing unexpected credentials, tokens, or configuration fragments
Diagnostic logs, crash dumps, or serialized payloads that include fields intended to be redacted
Unusual client requests probing endpoints that return verbose responses or error details

Detection Strategies

Inspect application responses and logs for sensitive data patterns such as authentication tokens, connection strings, and internal identifiers
Run data loss prevention rules against traffic egressing from services built on affected .NET versions
Compare installed .NET runtime and SDK versions against the fixed builds listed in Microsoft's advisory

Monitoring Recommendations

Enable structured logging on .NET services and monitor for fields that should be redacted appearing in transferred payloads
Track network flows from application servers to external destinations for size or content anomalies
Alert on repeated requests to endpoints known to serialize complex objects or return error details

How to Mitigate CVE-2026-62900

Immediate Actions Required

Apply the .NET security update referenced in the Microsoft Security Update Guide to all affected hosts
Inventory applications built on affected .NET runtimes and prioritize internet-facing services
Rotate any credentials, tokens, or secrets that may have transited through vulnerable code paths

Patch Information

Microsoft has released updates addressing CVE-2026-62900. Consult the Microsoft Security Update Guide for the exact runtime and SDK versions that contain the fix and follow standard .NET patching procedures for your deployment model.

Workarounds

Restrict network access to services running vulnerable .NET versions until patches are applied
Disable verbose error responses and detailed exception output on production endpoints
Add egress filtering or response scrubbing at reverse proxies to strip sensitive fields from outbound traffic

bash

# Verify installed .NET runtimes and SDKs, then update to a fixed version
dotnet --list-runtimes
dotnet --list-sdks

# On Windows, apply the corresponding Microsoft security update
# On Linux, update via the package manager, for example:
sudo apt-get update && sudo apt-get install --only-upgrade dotnet-runtime-8.0 dotnet-sdk-8.0