Vulnerability-Lookup

CVE-2026-76840 (GCVE-0-2026-76840)

Vulnerability from cvelistv5 – Published: 2026-08-24 13:11 – Updated: 2026-08-24 16:27

Title

RustDesk through 1.4.9 Heap Buffer Overflow via Unvalidated CLIPRDR FileContentsResponse Length

Summary

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.

Severity

8.5 (High)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:L/SI:H/SA:H

9.6 (Critical)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:H

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-24 16:26 UTC

CWE

CWE-787 - Out-of-bounds Write
CWE-20 - Improper Input Validation

Assigner

VulnCheck mitre root

References

5 references

URL	Tags
https://github.com/rustdesk/rustdesk	product
https://github.com/rustdesk/rustdesk/blob/1.4.9/l…	technical-description
https://github.com/rustdesk/rustdesk/pull/15515	issue-tracking
https://github.com/FreeRDP/FreeRDP/security/advis…	third-party-advisory
https://www.vulncheck.com/advisories/rustdesk-thr…	third-party-advisory

Impacted products

1 product

Vendor	Product	Version	CPE status
rustdesk	rustdesk	Affected: 0 , ≤ 1.4.9 (semver)	guessed

Date Public

2026-08-18 00:00

Credits

Michael Holmquist

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-76840

Vulnerability from fkie_nvd - Published: 2026-08-24 14:17 - Updated: 2026-08-24 17:18

Severity

9.6 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:H

Summary

References

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

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "collectionURL": "https://github.com/rustdesk/rustdesk",
          "defaultStatus": "unaffected",
          "packageName": "rustdesk",
          "product": "rustdesk",
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              "versionType": "semver"
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  ],
  "cveTags": [],
  "descriptions": [
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      "lang": "en",
      "value": "RustDesk\u0027s 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-\u003ereq_fdata, clipboard-\u003ereq_fsize), where req_fsize is taken verbatim from the peer\u0027s CLIPRDR FileContentsResponse by wf_cliprdr_server_file_contents_response (req_fsize = fileContentsResponse-\u003ecbRequested) and is never clamped to cb anywhere in the chain. The function\u0027s only length comparison, req_fsize \u003c 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\u0027s heap buffer when the local user pastes clipboard file contents offered by the remote side. The file is a fork of FreeRDP\u0027s client/Windows/wf_cliprdr.c, where the same defect is CVE-2026-68579, fixed in FreeRDP 3.30.0."
    }
  ],
  "id": "CVE-2026-76840",
  "lastModified": "2026-08-24T17:18:17.950",
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          "exploitMaturity": "NOT_DEFINED",
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          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
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    }
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  "vulnStatus": "Received",
  "weaknesses": [
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        {
          "lang": "en",
          "value": "CWE-20"
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          "lang": "en",
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}

GHSA-8M44-J2JR-WMRP

Vulnerability from github – Published: 2026-08-24 15:31 – Updated: 2026-08-24 15:31

Details

Severity

9.6 (Critical)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:H

8.5 (High)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:L/SI:H/SA:H

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-76840"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-20"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-24T14:17:01Z",
    "severity": "HIGH"
  },
  "details": "RustDesk\u0027s 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-\u003ereq_fdata, clipboard-\u003ereq_fsize), where req_fsize is taken verbatim from the peer\u0027s CLIPRDR FileContentsResponse by wf_cliprdr_server_file_contents_response (req_fsize = fileContentsResponse-\u003ecbRequested) and is never clamped to cb anywhere in the chain. The function\u0027s only length comparison, req_fsize \u003c 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\u0027s heap buffer when the local user pastes clipboard file contents offered by the remote side. The file is a fork of FreeRDP\u0027s client/Windows/wf_cliprdr.c, where the same defect is CVE-2026-68579, fixed in FreeRDP 3.30.0.",
  "id": "GHSA-8m44-j2jr-wmrp",
  "modified": "2026-08-24T15:31:51Z",
  "published": "2026-08-24T15:31:51Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-m37j-jcr2-8gcc"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-76840"
    },
    {
      "type": "WEB",
      "url": "https://github.com/rustdesk/rustdesk/pull/15515"
    },
    {
      "type": "WEB",
      "url": "https://github.com/rustdesk/rustdesk"
    },
    {
      "type": "WEB",
      "url": "https://github.com/rustdesk/rustdesk/blob/1.4.9/libs/clipboard/src/windows/wf_cliprdr.c"
    },
    {
      "type": "WEB",
      "url": "https://www.vulncheck.com/advisories/rustdesk-through-heap-buffer-overflow-via-unvalidated-cliprdr-filecontentsresponse-length"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/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",
      "type": "CVSS_V4"
    }
  ]
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

CVE-2026-76840 (GCVE-0-2026-76840)

FKIE_CVE-2026-76840

GHSA-8M44-J2JR-WMRP

Tags

Sightings

Nomenclature