Vulnerability 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.
CVSS Score
CRITICAL
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Freerdp | Freerdp | < 3.28.0 |
Related Weaknesses (CWE)
References
- https://github.com/FreeRDP/FreeRDP/commit/1f7a716d39b5605bb8a83b0c3c97a6ce386609Patch
- https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-pjqx-v446-x7fcExploitMitigationVendor Advisory
- https://www.vulncheck.com/advisories/freerdp-before-heap-buffer-overflow-via-cryPatchThird Party Advisory
FAQ
What is CVE-2026-64620?
CVE-2026-64620 is a vulnerability with a CVSS score of 9.8 (CRITICAL). 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 call...
How severe is CVE-2026-64620?
CVE-2026-64620 has been rated CRITICAL with a CVSS base score of 9.8/10. This is considered a critical vulnerability requiring immediate attention.
Is there a patch for CVE-2026-64620?
Check the references section above for vendor advisories and patch information. Affected products include: Freerdp Freerdp.