CVE-2026-26955
Description
A flaw was found in FreeRDP, a free implementation of the Remote Desktop Protocol (RDP). A malicious RDP server can exploit a heap buffer overflow vulnerability by sending a specially crafted graphics command to a FreeRDP client. This allows the server to write data outside of its intended memory region, potentially leading to arbitrary code execution on the client system. The vulnerability occurs because the client does not properly validate the dimensions of incoming graphics commands.
Statement
A malicous RDP server may lead a heap buffer overflow in FreeRDP when the client is using the GDI surface pipeline. This happens when the server send a maliciously crafted RDPGFX ClearCodec command. When interpreting the command FreeRDP fails to validate the whether rectangle described by it falls within the destination surface dimension allowing the attacker to overwrite the surface data buffer without any boundaries check. Depending on the memory layout of the freerdp client's process it's possible to corrupt adjacent points leading to a remote code execution or force the freerdp client to crash.
Mitigation
To mitigate this issue, avoid connecting to untrusted or unverified RDP servers. Users should only establish RDP connections with known and trusted servers. If connecting to untrusted servers is unavoidable, consider using a sandbox environment or a dedicated, isolated system for such connections to limit potential impact.
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 | 8.8 | N/A | 8.8 |
| 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 | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability
Technical Impact: Read Memory; Modify Memory; Execute Unauthorized Code or Commands
Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of a program'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 program into an infinite loop.
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
