CVE-2026-64620 FreeRDP before 3.28.0 Heap Buffer Overflow via crypto_rsa_common
An unauthenticated attacker can cause a heap buffer overflow in FreeRDP servers using Standard Security, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-64620?
CVE-2026-64620 is a critical memory corruption vulnerability in Freerdp Freerdp, published on 20 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Weakness: CWE-122
Which versions are affected by CVE-2026-64620?
It affects 1 product.
Products include Freerdp Freerdp.
How do I fix CVE-2026-64620?
Upgrade to a fixed version.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-64620 being exploited?
There is no known exploitation of CVE-2026-64620 in the wild and no public exploit code.
Other vulnerabilities in Freerdp Freerdp
- CVE-2021-37594 Other in n/a
- CVE-2021-37595 Other in n/a
- CVE-2026-67305 FreeRDP Windows Client before 3.29.0 Heap Buffer Overflow via Cliprdr
- CVE-2026-66402 FreeRDP before 3.29.0 TLS Certificate Identity Validation Bypass
- CVE-2026-67289 FreeRDP before 3.29.0 HTTP Proxy Request Injection via Redirection
Sources
Also known as DEBIAN-CVE-2026-64620, GHSA-pjqx-v446-x7fc, GHSA-xmhx-cqxp-qrgq, MINI-c997-q4fh-pxw9, UBUNTU-CVE-2026-64620.