1. Home
  2. Vulnerabilities
  3. CVE-2026-76840
9.6
CRITICAL CVSS 3.1
CVE-2026-76840
RustDesk through 1.4.9 Heap Buffer Overflow via Unvalidated CLIPRDR FileContentsResponse Length
Overview
Description

RustDesk's Windows clipboard redirection copies a peer-supplied length into a fixed-size caller buffer without an upper bound check. When an OLE paste consumer such as explorer.exe calls IStream::Read with a buffer of cb bytes, CliprdrStream_Read in libs/clipboard/src/windows/wf_cliprdr.c requests that many bytes of a remote file through cliprdr_send_request_filecontents and then executes CopyMemory(pv, clipboard->req_fdata, clipboard->req_fsize), where req_fsize is taken verbatim from the peer's CLIPRDR FileContentsResponse by wf_cliprdr_server_file_contents_response (req_fsize = fileContentsResponse->cbRequested) and is never clamped to cb anywhere in the chain. The function's only length comparison, req_fsize < cb, handles the short-read case and is evaluated after the copy has already occurred. A malicious or compromised peer that answers a small file-contents read with an oversized response therefore writes attacker-chosen data past the end of the paste consumer's heap buffer when the local user pastes clipboard file contents offered by the remote side. The file is a fork of FreeRDP's client/Windows/wf_cliprdr.c, where the same defect is CVE-2026-68579, fixed in FreeRDP 3.30.0.

Details
INFO

Published Date :

Aug. 24, 2026, 2:17 p.m.

Last Modified :

Oct. 14, 2026, 1:10 p.m.

Remotely Exploit :

Yes !

Source :

[email protected]
Impact
Affected Products

The following products are affected by CVE-2026-76840 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID Vendor Product Action
1 Rustdesk rustdesk
: Total Affected Vendor : 1 | Products : 1
Scoring
CVSS Scores
The Common Vulnerability Scoring System is a standardized framework for assessing the severity of vulnerabilities in software and systems. We collect and displays CVSS scores from various sources for each CVE.
Score Version Severity Vector Exploitability Score Impact Score Source
CVSS 134c704f-9b21-4f2e-91b3-4a467353bcc0
CVSS 3.1 CRITICAL 83251b91-4cc7-4094-a5c7-464a1b83ea10
CVSS 3.1 CRITICAL [email protected]
CVSS 3.1 CRITICAL MITRE-CVE
CVSS 4.0 HIGH 83251b91-4cc7-4094-a5c7-464a1b83ea10
CVSS 4.0 HIGH [email protected]
Solution
Update RustDesk to patch the buffer overflow vulnerability in clipboard redirection.
  • Update RustDesk to the latest version.
  • Apply vendor patches for clipboard handling.
  • Validate clipboard data lengths rigorously.
  • Avoid pasting remote clipboard content.
References
References to Advisories, Solutions, and Tools

Here, you will find a curated list of external links that provide in-depth information, practical solutions, and valuable tools related to CVE-2026-76840.

URL Resource
https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-m37j-jcr2-8gcc
https://github.com/rustdesk/rustdesk
https://github.com/rustdesk/rustdesk/blob/1.4.9/libs/clipboard/src/windows/wf_cliprdr.c
https://github.com/rustdesk/rustdesk/pull/15515
https://www.vulncheck.com/advisories/rustdesk-through-heap-buffer-overflow-via-unvalidated-cliprdr-filecontentsresponse-length
CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-76840 is associated with the following CWEs:

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-76840 weaknesses.

CAPEC-3: Using Leading 'Ghost' Character Sequences to Bypass Input Filters Using Leading 'Ghost' Character Sequences to Bypass Input Filters CAPEC-7: Blind SQL Injection Blind SQL Injection CAPEC-8: Buffer Overflow in an API Call Buffer Overflow in an API Call CAPEC-9: Buffer Overflow in Local Command-Line Utilities Buffer Overflow in Local Command-Line Utilities CAPEC-10: Buffer Overflow via Environment Variables Buffer Overflow via Environment Variables CAPEC-13: Subverting Environment Variable Values Subverting Environment Variable Values CAPEC-14: Client-side Injection-induced Buffer Overflow Client-side Injection-induced Buffer Overflow CAPEC-22: Exploiting Trust in Client Exploiting Trust in Client CAPEC-23: File Content Injection File Content Injection CAPEC-24: Filter Failure through Buffer Overflow Filter Failure through Buffer Overflow CAPEC-28: Fuzzing Fuzzing CAPEC-31: Accessing/Intercepting/Modifying HTTP Cookies Accessing/Intercepting/Modifying HTTP Cookies CAPEC-42: MIME Conversion MIME Conversion CAPEC-43: Exploiting Multiple Input Interpretation Layers Exploiting Multiple Input Interpretation Layers CAPEC-45: Buffer Overflow via Symbolic Links Buffer Overflow via Symbolic Links CAPEC-46: Overflow Variables and Tags Overflow Variables and Tags CAPEC-47: Buffer Overflow via Parameter Expansion Buffer Overflow via Parameter Expansion CAPEC-52: Embedding NULL Bytes Embedding NULL Bytes CAPEC-53: Postfix, Null Terminate, and Backslash Postfix, Null Terminate, and Backslash CAPEC-63: Cross-Site Scripting (XSS) Cross-Site Scripting (XSS) CAPEC-64: Using Slashes and URL Encoding Combined to Bypass Validation Logic Using Slashes and URL Encoding Combined to Bypass Validation Logic CAPEC-67: String Format Overflow in syslog() String Format Overflow in syslog() CAPEC-71: Using Unicode Encoding to Bypass Validation Logic Using Unicode Encoding to Bypass Validation Logic CAPEC-72: URL Encoding URL Encoding CAPEC-73: User-Controlled Filename User-Controlled Filename CAPEC-78: Using Escaped Slashes in Alternate Encoding Using Escaped Slashes in Alternate Encoding CAPEC-79: Using Slashes in Alternate Encoding Using Slashes in Alternate Encoding CAPEC-80: Using UTF-8 Encoding to Bypass Validation Logic Using UTF-8 Encoding to Bypass Validation Logic CAPEC-81: Web Server Logs Tampering Web Server Logs Tampering CAPEC-83: XPath Injection XPath Injection CAPEC-85: AJAX Footprinting AJAX Footprinting CAPEC-88: OS Command Injection OS Command Injection CAPEC-101: Server Side Include (SSI) Injection Server Side Include (SSI) Injection CAPEC-104: Cross Zone Scripting Cross Zone Scripting CAPEC-108: Command Line Execution through SQL Injection Command Line Execution through SQL Injection CAPEC-109: Object Relational Mapping Injection Object Relational Mapping Injection CAPEC-110: SQL Injection through SOAP Parameter Tampering SQL Injection through SOAP Parameter Tampering CAPEC-120: Double Encoding Double Encoding CAPEC-135: Format String Injection Format String Injection CAPEC-136: LDAP Injection LDAP Injection CAPEC-153: Input Data Manipulation Input Data Manipulation CAPEC-182: Flash Injection Flash Injection CAPEC-209: XSS Using MIME Type Mismatch XSS Using MIME Type Mismatch CAPEC-230: Serialized Data with Nested Payloads Serialized Data with Nested Payloads CAPEC-231: Oversized Serialized Data Payloads Oversized Serialized Data Payloads CAPEC-250: XML Injection XML Injection CAPEC-261: Fuzzing for garnering other adjacent user/sensitive data Fuzzing for garnering other adjacent user/sensitive data CAPEC-267: Leverage Alternate Encoding Leverage Alternate Encoding CAPEC-473: Signature Spoof Signature Spoof CAPEC-588: DOM-Based XSS DOM-Based XSS CAPEC-664: Server Side Request Forgery Server Side Request Forgery

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2026-76840 vulnerability anywhere in the article.

Results are limited to the first 20 news articles due to potential performance issues.

The following table lists the changes that have been made to the CVE-2026-76840 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

  • CVE Translated by [email protected]

    Oct. 14, 2026

    Action Type Old Value New Value
    Added Translation Title: RustDesk, Description: La redirección del portapapeles de Windows de RustDesk copia una longitud proporcionada por el par en un búfer de llamador de tamaño fijo sin una comprobación de límite superior. Cuyo un consumidor de pegado OLE como explorer.exe llama a IStream::Read con un búfer de cb bytes, CliprdrStream_Read en libs/clipboard/src/windows/wf_cliprdr.c solicita esa cantidad de bytes de un archivo remoto a través de cliprdr_send_request_filecontents y luego ejecuta CopyMemory(pv, clipboard -> req_fdata, clipboard -> req_fsize), donde req_fsize se toma textualmente de la respuesta CLIPRDR FileContentsResponse del par por wf_cliprdr_server_file_contents_response (req_fsize = fileContentsResponse -> cbRequested) y nunca se ajusta a cb en ningún lugar de la cadena. La única comparación de longitud de la función, req_fsize < cb, maneja el caso de lectura corta y se evalúa después de que la copia ya ha ocurrido. Un par malicioso o comprometido que responde a una lectura pequeña de contenido de archivo con una respuesta sobredimensionada, por lo tanto, escribe datos elegidos por el atacante más allá del final del búfer de pila del consumidor de pegado cuyo el usuario local pega el contenido del archivo del portapapeles ofrecido por el lado remoto. El archivo es una bifurcación de client/Windows/wf_cliprdr.c de FreeRDP, donde el mismo defecto es CVE-2026-68579, corregido en FreeRDP 3.30.0.
  • CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Aug. 24, 2026

    Action Type Old Value New Value
    Added SSVC {'id': 'CVE-2026-76840', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-08-24T16:26:40.462428Z'}
  • New CVE Received by [email protected]

    Aug. 24, 2026

    Action Type Old Value New Value
    Added Affected [{'vendor': 'rustdesk', 'product': 'rustdesk', 'versions': [{'status': 'affected', 'version': '0', 'versionType': 'semver', 'lessThanOrEqual': '1.4.9'}], 'packageName': 'rustdesk', 'collectionURL': 'https://github.com/rustdesk/rustdesk', 'defaultStatus': 'unaffected'}]
    Added Description RustDesk's Windows clipboard redirection copies a peer-supplied length into a fixed-size caller buffer without an upper bound check. When an OLE paste consumer such as explorer.exe calls IStream::Read with a buffer of cb bytes, CliprdrStream_Read in libs/clipboard/src/windows/wf_cliprdr.c requests that many bytes of a remote file through cliprdr_send_request_filecontents and then executes CopyMemory(pv, clipboard->req_fdata, clipboard->req_fsize), where req_fsize is taken verbatim from the peer's CLIPRDR FileContentsResponse by wf_cliprdr_server_file_contents_response (req_fsize = fileContentsResponse->cbRequested) and is never clamped to cb anywhere in the chain. The function's only length comparison, req_fsize < cb, handles the short-read case and is evaluated after the copy has already occurred. A malicious or compromised peer that answers a small file-contents read with an oversized response therefore writes attacker-chosen data past the end of the paste consumer's heap buffer when the local user pastes clipboard file contents offered by the remote side. The file is a fork of FreeRDP's client/Windows/wf_cliprdr.c, where the same defect is CVE-2026-68579, fixed in FreeRDP 3.30.0.
    Added CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:L/SI:H/SA:H/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:X/V:X/RE:X/U:X
    Added CVSS V3.1 AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:H
    Added CWE CWE-20
    Added CWE CWE-787
    Added Reference https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-m37j-jcr2-8gcc
    Added Reference https://github.com/rustdesk/rustdesk
    Added Reference https://github.com/rustdesk/rustdesk/blob/1.4.9/libs/clipboard/src/windows/wf_cliprdr.c
    Added Reference https://github.com/rustdesk/rustdesk/pull/15515
    Added Reference https://www.vulncheck.com/advisories/rustdesk-through-heap-buffer-overflow-via-unvalidated-cliprdr-filecontentsresponse-length
EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.
CVSS
Vulnerability Scoring Details
Base CVSS Score: 8.5
Attack Vector
Attack Complexity
Attack Requirements
Privileges Required
User Interaction
VS Confidentiality
VS Integrity
VS Availability
SS Confidentiality
SS Integrity
SS Availability
Base CVSS Score: 9.6
Attack Vector
Attack Complexity
Privileges Required
User Interaction
Scope
Confidentiality Impact
Integrity Impact
Availability Impact