CVE-2026-64620

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure, data tampering, service disruption.

Exploit odds

0.9% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-07-20 12:19 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-07-28 15:38 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.9% in the next 30 days (EPSS).
• Severity: 9.3 CRITICAL (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-07-20 12:19 UTC

Last modified

2026-07-28 15:38 UTC

Exploit probability

0.9% · EPSS, next 30 days

Weakness

CWE-122

Record status

Analyzed

Affected

• Freerdp < 3.28.0

Attack profile CVSS 4.0 · 9.3

Attack vector

Network

Complexity

Low

Attack requirements

None

Privileges needed

None

User interaction

None

Confidentiality

High

Integrity

High

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-64620.md and follow it. Check whether this project is affected by CVE-2026-64620. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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