A buffer overflow occurs on the server side when decrypting a client‑supplied random value using RSA. The crypto_rsa_common function writes the result of a modular exponentiation into the caller's buffer before performing a bounds check, allowing an attacker to overflow a 32‑byte heap buffer with up to 224 bytes of data. The overflow can corrupt heap memory and cause the server to crash, resulting in a denial‑of‑service condition before any authentication has taken place. This flaw is a classic example of CWE‑122, a heap‑buffer overflow vulnerability.

Versions of FreeRDP up to and including 3.27.1 are affected. The vulnerability resides in e.g. 3.27.1 and earlier releases of the FreeRDP project. Any deployment of FreeRDP that uses a pre‑3 build, regardless of platform, is subject to this flaw.

The CVSS score of 9.3 indicates a critical severity. The EPSS score of 0.00578 (approximately 0.58%) shows a low probability of exploitation at this time. The lack of a KEV listing suggests publicly known exploits are not yet widespread. The vulnerability is triggered before authentication and can be leveraged by sending crafted RDP packets that cause the server to decrypt an attacker‑crafted ciphertext. This leads to a heap buffer overflow that can crash the server, causing a denial‑of‑service. Because the overflow writes to heap memory, there is a theoretical risk of arbitrary code execution if an attacker can chain the overflow with further payloads, but no remote code execution has been reported.