CVE-2026-121397
Description
A flaw was found in FreeRDP. A malicious Remote Desktop Protocol (RDP) server can cause an information disclosure by sending crafted clipboard image data to a connected client. When the client converts the image into Portable Network Graphics (PNG) format, a heap buffer over-read occurs, embedding sensitive client heap memory into the resulting image.
Statement
This vulnerability is rated as Moderate impact because successful exploitation requires a user to connect to an untrusted RDP server, and the resulting memory over-read leaks client heap data rather than allowing arbitrary code execution or system compromise. In Red Hat enterprise environments, FreeRDP is typically deployed as an interactive client application or embedded library for remote desktop connectivity. The flaw can only be triggered during active remote desktop sessions where clipboard synchronization is enabled and incoming graphical clipboard content is processed. Consequently, exposure is limited to targeted user-driven sessions with untrusted remote endpoints.
Mitigation
Disable clipboard synchronization in RDP client connections:
1. When running command-line FreeRDP sessions, do not enable clipboard redirection (omit `+clipboard` or `/clipboard`, or explicitly pass `-clipboard`).
2. In graphical remote desktop managers that utilize FreeRDP (such as Remmina), disable clipboard synchronization in the connection profile settings under session options.
3. Avoid initiating remote desktop sessions to untrusted or unverified hosts.
Caveats: Disabling clipboard synchronization prevents copying and pasting data, including text and images, between the local desktop and the remote session.
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).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 4.3 | N/A | 4.3 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | Required | N/A | Required |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | Low | N/A | Low |
| Integrity Impact | None | N/A | None |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Memory
An attacker could get secret values such as cryptographic keys, PII, memory addresses, or other information that could be used in additional attacks.
Confidentiality
Technical Impact: Bypass Protection Mechanism
Out-of-bounds memory could contain memory addresses or other information that can be used to bypass ASLR and other protection mechanisms in order to improve the reliability of exploiting a separate weakness for code execution.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
An attacker could cause a segmentation fault or crash by causing memory to be read outside of the bounds of the buffer. This is especially likely when the code reads a variable amount of data and assumes that a sentinel exists to stop the read operation, such as a NUL in a string.
Other
Technical Impact: Varies by Context
The read operation could produce other undefined or unexpected results.
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