CVE-2026-56297
Description
A flaw was found in FreeRDP. A malicious Remote Desktop Protocol (RDP) server can exploit a use-after-free vulnerability due to improper synchronization of channel callback access. By sending DYNVC_DATA and DYNVC_CLOSE messages concurrently, a race condition can be triggered in the drdynvc client thread, leading to heap-use-after-free. This could potentially enable remote code execution or cause a denial of service.
Statement
This Moderate impact flaw in FreeRDP allows a malicious RDP server to trigger a use-after-free condition on the client by exploiting a race condition during dynamic virtual channel closure. This could lead to remote code execution or denial of service on the client system when connecting to a compromised or untrusted RDP server.
Mitigation
Configure host-based firewalls (e.g., firewalld) or network egress filtering so that the workstation can only initiate outbound RDP connections (typically TCP 3389) to known, trusted internal RDP gateways or corporate servers. Blocking outbound RDP to the wider internet neutralizes the threat of users accidentally connecting to malicious external endpoints.
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 | 5.6 | 8.1 | 7 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | High | High | High |
| Privileges Required | None | None | None |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | Low | High | Low |
| Integrity Impact | Low | High | Low |
| Availability Impact | Low | High | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
NVD: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability
Technical Impact: Modify Application Data; Modify Memory; DoS: Crash, Exit, or Restart; Execute Unauthorized Code or Commands
It may be possible to cause data corruption and possibly execute arbitrary code by modifying global variables or data structures at unexpected times, violating the assumptions of code that uses this global data.
Access Control
Technical Impact: Gain Privileges or Assume Identity
If a signal handler interrupts code that is executing with privileges, it may be possible that the signal handler will also be executed with elevated privileges, possibly making subsequent exploits more severe.
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