CVE-2026-45657 — Windows 11 23h2
CRITICALCVE-2026-45657 is a critical-severity (CVSS 9.8) CWE-122 vulnerability in microsoft windows 11 23h2. A fix is available — see the affected versions and patch details below.
Use after free in Windows Kernel allows an unauthorized attacker to execute code over a network.
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
- 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-2026-45657.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-45657 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,386 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Description
Use after free in Windows Kernel allows an unauthorized attacker to execute code over a network.
Affected Products
windows 11 23h2microsoftwindows 11 24h2microsoftwindows 11 25h2microsoftwindows 11 26h1microsoftwindows server 2022microsoftwindows server 2025microsoftDetection & mitigation playbook
Vendor / applianceDetect
Inventory every microsoft windows 11 23h2 deployment and check each version against the affected-products list above.
Fix
Apply the microsoft windows 11 23h2 security patch or hotfix for CVE-2026-45657 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-2026-45657 being exploited in your environment?
Detect and block the exploit chain at execution, on systems you cannot patch yet.