Vulnerability record · CVE-2026-64620 · published 20 July 2026
CVE-2026-64620: Freerdp heap-based buffer overflow vulnerability
Freerdp · Freerdp
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.
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:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:
Affected products
1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.
References
| Link | Tags |
|---|---|
| https://github.com/FreeRDP/FreeRDP/commit/1f7a716d39b5605bb8a83b0c3c97a6ce386609ef | Patch |
| https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-pjqx-v446-x7fc | ExploitMitigationVendor Advisory |
| https://www.vulncheck.com/advisories/freerdp-before-heap-buffer-overflow-via-crypto-rsa-common | PatchThird Party Advisory |
Track CVE-2026-64620 inside VULONE
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Related vulnerabilities
Same products first, then exploited flaws of the same weakness class.
Source: NIST National Vulnerability Database (record CVE-2026-64620), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.
