CVE-2026-64620Public exploitNetwork attack vector

Pre-auth server crash via late RSA bounds check

Published Jul 20, 2026 · Updated Jul 20, 2026

Heap-based buffer overflow in FreeRDP before 3.28.0 allows remote attackers to crash RDP servers before authentication. crypto_rsa_common() calls BN_bn2bin() into the caller's 32-byte ClientRandom buffer before comparing the result length with the buffer capacity. Reachability requires a FreeRDP-based server that permits RDP Standard Security; the demonstrated consequence is a pre-authentication server crash.

CVSS severity9.3
Critical
EPSS probability0.85%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-based buffer overflow in FreeRDP before 3.28.0 allows remote attackers to crash RDP servers before authentication. crypto_rsa_common() calls BN_bn2bin() into the caller's 32-byte ClientRandom buffer before comparing the result length with the buffer capacity. Reachability requires a FreeRDP-based server that permits RDP Standard Security; the demonstrated consequence is a pre-authentication server crash.

The record

CVE
CVE-2026-64620
Published
Jul 20, 2026
Updated
Jul 20, 2026
Vendor
FreeRDP
Product
FreeRDP
Classifications
CWE-122, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 20, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 20, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <3.28.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

FreeRDP · FreeRDPversion=0 <3.28.0

Published CVSS scores

9.3VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
9.8VulnCheckCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.1NISTCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-122Heap-based Buffer Overflow
T1499Endpoint Denial of Service

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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