CVE-2026-64620
Description
A heap-based buffer overflow in FreeRDP's crypto_rsa_common() allows an unauthenticated remote attacker to trigger a denial of service or potential remote code execution. By sending a crafted ciphertext during RDP Standard Security key establishment, the attacker can force a data write before the size is validated, resulting in memory corruption.
Statement
An unauthenticated remote attacker can trigger a heap buffer overflow in FreeRDP by sending a crafted ciphertext during key establishment.
Red Hat rates this vulnerability as Important rather than Critical due to inherent mitigations in Red Hat environments. Specifically, RHEL's built-in memory defenses (such as glibc heap hardening) reliably reduce the threat of remote code execution down to a localized service crash (Denial of Service). Furthermore, the flaw is only reachable if an administrator explicitly configures the server to use the non-default, legacy "RDP Standard Security.
Mitigation
To mitigate, explicitly disable legacy RDP Standard Security and enforce Network Level Authentication (NLA/TLS) on the server. Additionally, restrict network access to trusted clients via firewalls, or disable the FreeRDP service entirely if not needed, remembering to restart the service to apply any configuration changes.
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 | 8.1 | 9.1 | 9.8 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | High | Low | Low |
| Privileges Required | None | None | None |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | High | None | High |
| Integrity Impact | High | High | High |
| Availability Impact | High | High | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands
Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of the product's implicit security policy. This can often be used to subvert any other security service.
Availability
Technical Impact: Modify Memory; DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU)
Buffer overflows generally lead to crashes. Other attacks leading to lack of availability are possible, including putting the product into an infinite loop.
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