CVE-2026-77896 — Windows 10 21h2
MEDIUMCVE-2026-77896 is a medium-severity (CVSS 6.5) CWE-190 vulnerability in microsoft windows 10 21h2. A fix is available — see the affected versions and patch details below.
Integer overflow or wraparound in Remote Desktop Client allows an unauthorized attacker to deny service over a network.
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-77896.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-77896 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 380,066 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Description
Integer overflow or wraparound in Remote Desktop Client allows an unauthorized attacker to deny service over a network.
Affected Products
windows 10 21h2microsoftwindows 10 22h2microsoftwindows 10 1607microsoftwindows 10 1809microsoftwindows 11 23h2microsoftwindows 11 24h2microsoftDetection & mitigation playbook
Vendor / applianceDetect
Inventory every microsoft windows 10 21h2 deployment and check each version against the affected-products list above.
Fix
Apply the microsoft windows 10 21h2 security patch or hotfix for CVE-2026-77896 on the affected version, following the vendor advisory for your exact build.
Workarounds
Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.
Frequently Asked Questions
Is CVE-2026-77896 being exploited in your environment?
Detect and block the exploit chain at execution, on systems you cannot patch yet.