CVE-2026-64620
CriticalCVSS 9.8Exploitation Probability (EPSS)
Low risk44th percentile - higher than 44% of all known CVEs
Summary
A heap-based buffer overflow in FreeRDP before version 3.28.0 (affected <=3.27.1) in the crypto_rsa_common() function. The function writes the modular exponentiation result to the output buffer before checking bounds, allowing out-of-bounds writes.
Risk Assessment
An unauthenticated attacker can send a forged ciphertext that, when decrypted, overflows the 32-byte heap buffer by up to ~224 bytes, causing denial of service.
Recommendation
It is recommended to upgrade FreeRDP to version 3.28.0 or later, which fixes this vulnerability.
Original NVD description (English source)
FreeRDP before 3.28.0 (affected <=3.27.1) contains a heap-based buffer overflow in crypto_rsa_common() (libfreerdp/crypto/crypto.c). The function writes the modular-exponentiation result into the caller's output buffer via BN_bn2bin() and only afterward checks output_length > out_length, so out-of-bounds bytes are written before the bounds check. On the server side, when a client selects RDP Standard Security, the encrypted client random is decrypted into a fixed 32-byte buffer. Because the server publishes its RSA public key, an unauthenticated attacker can forge a ciphertext whose decrypted value is up to the full modulus length (e.g. 256 bytes for RSA-2048), overflowing the 32-byte heap buffer by up to ~224 attacker-controlled bytes pre-authentication, resulting in denial of service.