CVE-2026-66822
Description
Insertion of sensitive information into sent data in .NET allows an unauthorized attacker to disclose information over a network.
Statement
A moderate information disclosure vulnerability was found in the .NET runtime. When a .NET application using SocketsHttpHandler sends a request through a proxy that authenticates with basic credentials and the response is an HTTP redirect, the Proxy-Authorization header can be incorrectly retained and forwarded with the redirected request, leaking the basic proxy credentials to the destination server. This allows an unauthorized remote attacker to disclose sensitive proxy authentication information over a network. Red Hat rates this flaw Moderate severity with a CVSS 3.1 base score of 5.9 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N), consistent with the upstream assessment. All currently tracked Red Hat product streams shipping the affected dotnet8.0, dotnet9.0, and dotnet10.0 components, including Red Hat Enterprise Linux and Red Hat Hardened Images, are affected, and fixes are being pursued through the respective product channels.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.9 | N/A | 5.9 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | None | N/A | None |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C
Red Hat CVSS v3 Score Explanation
Microsoft CNA CVSS from pre-release advisory
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Files or Directories; Read Memory; Read Application Data
Sensitive data may be exposed to attackers.
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