CVE-2026-64620FreeRDP before 3.28.0 Heap Buffer Overflow via crypto_rsa_common

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• GitHub Security Advisory (GHSA-pjqx-v446-x7fc) vendor-advisory
• Patch Commit patch
• VulnCheck Advisory: FreeRDP before 3.28.0 Heap Buffer Overflow via crypto_rsa_common third-party-advisory