CVE-2026-91963
Description
A flaw was found in FreeRDP. An uninitialized heap memory disclosure vulnerability exists in the urbdrc USB redirection channel. A malicious Remote Desktop Protocol (RDP) server can exploit this by inducing failing USB transfers, allowing it to read uninitialized heap memory from the client. This information disclosure can defeat Address Space Layout Randomization (ASLR), potentially enabling remote code execution when chained with other memory corruption vulnerabilities.
Mitigation
To reduce exposure, avoid connecting to untrusted RDP servers or disable the FreeRDP USB redirection channel if it is not required. When using the `xfreerdp` client, ensure that USB redirection is not enabled. This can be done by omitting the `/usb` or `/usb-redir` command-line options, or by explicitly disabling the `urbdrc` channel through FreeRDP configuration if available. Disabling this feature will prevent the redirection of USB devices to 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).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.8 | N/A | 6.5 |
| 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 | None |
| Availability Impact | High | N/A | None |
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:N/A:N
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Memory
If the uninitialized pointer is used in a read operation, an attacker might be able to read sensitive portions of memory.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
If the uninitialized pointer references a memory location that is not accessible to the product, or points to a location that is "malformed" (such as NULL) or larger than expected by a read or write operation, then a crash may occur.
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
If the uninitialized pointer is used in a function call, or points to unexpected data in a write operation, then code execution may be possible.
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