Vulnerability Snapshot
CVE-2026-76840 is rated CRITICAL — exploitation is trivial or already observed in the wild and impact is severe. Patch immediately, not on the next maintenance window.
Executive 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
Why It Matters
CVE-2026-76840 is rated CRITICAL severity, requiring immediate attention from security teams.
CVSS Base Score: 9.6/10
🛡️What Defenders Should Check
Use Vulnios to continuously monitor your exposure to CVE-2026-76840 and similar vulnerabilities.
References & Sources
How Vulnios Detects This
Vulnios scans for this vulnerability using Trivy and Grype for SBOM-based CVE matching and Vulnios CVE feed continuous monitoring against your asset inventory. Run a scan against your environment to see whether you are exposed; findings are linked back to the original CVE record so triage starts with the patch path already known.
AI Security Advisor
Powered by Gemini
Get AI-powered security recommendations tailored to this specific threat — including risk assessment, detection guidance, MITRE ATT&CK mapping, and actionable remediation steps.
Sources
Related Threat Alerts
Frequently Asked Questions
What is CVE-2026-76840?
CVE-2026-76840 is a critical-severity vulnerability tracked under the Common Vulnerabilities and Exposures program. 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
Am I affected?
Affected technology is listed in the Affected Products section above. If your asset inventory contains any of them, assume in-scope until you can prove otherwise.
How urgent is the response?
Critical: do not wait for your normal patch cycle. Verify exposure today, apply the vendor patch immediately, and add detection rules for any post-exploit indicators.
How do I remediate?
Apply the vendor patch listed in the upstream advisory linked under Sources. If the patch is not yet available, follow the vendor-supplied workaround (often a config flag or feature disable) and add detections for the published exploit pattern in your SIEM. Re-scan after the patch lands to confirm the finding clears.
Where can I track exploitation activity?
Watch CISA's Known Exploited Vulnerabilities catalog for CVE-2026-76840. Cross-reference with public exploit databases and your own SIEM/IDS for indicator-of-compromise patterns. Vulnios tracks KEV status automatically and surfaces it on the asset findings view.
How does Vulnios help with this?
Vulnios continuously cross-references your asset inventory against the live CVE feed (NVD, vendor advisories, CISA KEV, and curated OSINT). When a new CVE matches your environment, you get a prioritized finding with the severity, KEV status, exploit-prediction (EPSS), and a direct path to the vendor patch. You can start a free scan from the homepage.
Protect Your Organization
Monitor CVEs, scan for vulnerabilities, and get real-time threat alerts — all in one platform.
Get instant alerts on Telegram
Join our public channel for real-time critical CVE alerts.
Follow @vulnios