Status: Resolved — September 14, 2026
An issue with a recent Windows update (KB5124008) that caused Cowork tasks — code execution, file read/write, search, and edit — to fail on Windows devices both inside and outside of Blue Border was resolved.
Duration: Approximately September 8, 2026 to September 14, 2026
Updates
September 17, 2026 — Resolved: Microsoft has confirmed, via its official Windows 11 release health documentation, that this issue was caused by Windows update KB5124008 and is resolved by installing the out-of-band update KB5129195 (released September 14, 2026) or any later cumulative update. If your organization uninstalled KB5124008 as a workaround, install KB5129195, and restart. This restores Cowork's sandbox functionality while keeping the critical patches for two actively exploited zero-day privilege elevation vulnerabilities (CVE-2026-81963 and CVE-2026-85880).
September 14, 2026 — Active: Issue identified and communicated.
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September 17, 2026 — Resolved: Microsoft has confirmed, via its official Windows 11 release health documentation, that this issue was caused by Windows update KB5124008 and is resolved by installing the out-of-band update KB5129195 (released September 14, 2026) or any later cumulative update. If your organization uninstalled KB5124008 as a workaround, install KB5129195, and restart. This restores Cowork's sandbox functionality while keeping the critical patches for two actively exploited zero-day privilege elevation vulnerabilities (CVE-2026-81963 and CVE-2026-85880).
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