CVE-2025-55248
Description
A flaw exists in certain .NET builds where a man-in-the-middle (MITM) attacker can prevent or downgrade TLS between a client and an SMTP server. This may cause the client to send credentials or message data over an unencrypted connection, exposing sensitive information to the attacker.
Statement
The Red Hat Product Security team has assessed the severity of this vulnerability as High, given that it can be remotely exploited by a man-in-the-middle attacker without authentication or user interaction. Successful exploitation allows an attacker to disable TLS protection between a .NET client and an SMTP server, leading to exposure of credentials and message contents over an unencrypted connection. The vulnerability results from insufficient enforcement of TLS during SMTP session negotiation in the affected .NET runtime.
.NET 6.0 for RHEL-8, RHEL-9 and RHIVOS has reached its End of Life as of November 12, 2024, and is no longer supported. No fixes will be provided for this stream. For additional information about lifecycle for .NET on Red Hat Enterprise Linux, please refer to: https://access.redhat.com/support/policy/updates/net-core”
Mitigation
Mitigation for this issue is either not available or the currently available options don't 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 | 8.2 | 5.7 | 4.8 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | Low | Low | High |
| Privileges Required | None | Low | Low |
| User Interaction | None | Required | Required |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | High | High | High |
| Integrity Impact | Low | None | None |
| Availability Impact | None | None | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N
NVD: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N
cve.org: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C
Understanding the Weakness (CWE)
Integrity,Confidentiality
Technical Impact: Read Application Data; Modify Files or Directories
Anyone can read the information by gaining access to the channel being used for communication. Many communication channels can be "sniffed" (monitored) by adversaries during data transmission. For example, in networking, packets can traverse many intermediary nodes from the source to the destination, whether across the internet, an internal network, the cloud, etc. Some actors might have privileged access to a network interface or any link along the channel, such as a router, but they might not be authorized to collect the underlying data. As a result, network traffic could be sniffed by adversaries, spilling security-critical data.
Integrity,Confidentiality
Technical Impact: Read Application Data; Modify Files or Directories; Other
When full communications are recorded or logged, such as with a packet dump, an adversary could attempt to obtain the dump long after the transmission has occurred and try to "sniff" the cleartext from the recorded communications in the dump itself. Even if the information is encoded in a way that is not human-readable, certain techniques could determine which encoding is being used, then decode the information.
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