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CVE-2026-76840— RustDesk through 1.4.9 Heap Buffer Overflow via Unvalidated CLIPRDR FileContentsResponse Length

Quick assessment

Affected
rustdesk rustdesk
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

RustDesk 的 Windows 剪贴板重定向功能在将远端提供的长度值复制到固定大小的调用者缓冲区时，未进行上界检查。当资源管理器（explorer.exe）等 OLE 粘贴消费者调用 并传入大小为 cb 字节的缓冲区时， 中的 函数会通过 请求获取相应数量的远程文件内容，随后执行 。其中， 直接取自远端发送的 （通过 设置： ），在整个处理链路中均未将其限制（clamp）为 cb 的上限。 该函数唯一的长度比较 仅用于处理读取数据不足的情况，且该比较在复制操作完成之后才进行评估。因此，当本地用户粘贴由远端提供

CVSS 9.6 · Critical EPSS 0.30% · P22

Possible ATT&CK Techniques 1 AI

T1059 · Command and Scripting Interpreter

Affected Version Matrix 1

VendorProduct Version RangeStatus
rustdesk rustdesk ≤ 1.4.9 affected
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I. Basic Information for CVE-2026-76840

Vulnerability Information
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Vulnerability Title
RustDesk through 1.4.9 Heap Buffer Overflow via Unvalidated CLIPRDR FileContentsResponse Length
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存写
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
rustdesk rustdesk 0 ~ 1.4.9 -

II. Public POCs for CVE-2026-76840

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 10760 chars
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III. Intelligence Information for CVE-2026-76840

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Patches & Fixes for CVE-2026-76840 (1)

Vendor Advisories for CVE-2026-76840 (1)

News Coverage for CVE-2026-76840 (1)

Vendor Pages for CVE-2026-76840 (1)

IV. Related Vulnerabilities

Same product: rustdesk
Same vendor: rustdesk
Same weakness: CWE-787

V. Comments for CVE-2026-76840

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