CVE-2026-40033Public exploitNetwork attack vector

Client code execution via clamped rectangle copy

Published May 26, 2026 · Updated May 26, 2026

Heap-buffer overflow in FreeRDP before 3.26.0 allows remote attackers to execute code or crash clients through crafted RDPGFX PDUs. The gdi_CacheToSurface handler validates a UINT16_MAX-clamped destination rectangle, then copies the original cache entry width and height into the surface buffer. Exploitation requires a client with RDPGFX enabled to connect to an attacker-controlled RDP server; successful writes can crash the client or execute code in its process.

CVSS severity8.8
High
EPSS probability1.04%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-buffer overflow in FreeRDP before 3.26.0 allows remote attackers to execute code or crash clients through crafted RDPGFX PDUs. The gdi_CacheToSurface handler validates a UINT16_MAX-clamped destination rectangle, then copies the original cache entry width and height into the surface buffer. Exploitation requires a client with RDPGFX enabled to connect to an attacker-controlled RDP server; successful writes can crash the client or execute code in its process.

The record

CVE
CVE-2026-40033
Published
May 26, 2026
Updated
May 26, 2026
Vendor
FreeRDP
Product
FreeRDP
Classifications
CWE-122, CWE-787, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 26, 2026CVE publishedPublication date reported by the CVE source.
  2. May 26, 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 <3.26.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

FreeRDP · FreeRDPversion=0 <3.26.0

Published CVSS scores

8.8FreeRDPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/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
CWE-787Out-of-bounds Write
T1203Exploitation for Client Execution

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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