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CVE-2026-64620

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).

Published Jul 20, 2026CWE-122EPSS 0.91%

Overview

CVE-2026-64620 is a critical-severity vulnerability. It was published on July 20, 2026 and has a CVSS 3.1 base score of 9.8 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.8, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/FreeRDP/FreeRDP/commit/1f7a716d39b5605bb8a83b0c3c97a6ce386609efGitHubgithub.com/FreeRDP/FreeRDP/security/advisories/GHSA-pjqx-v446-x7fcRefwww.vulncheck.com/advisories/freerdp-before-heap-buffer-overflow-via-crypto-rsa-common

How CyberStrike helps

Frequently asked questions

What is CVE-2026-64620?

CVE-2026-64620 is a critical-severity vulnerability. It was published on July 20, 2026 and has a CVSS 3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-64620?

This vulnerability has a CVSS 3.1 base score of 9.8, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-64620?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-64620?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-64620 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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