Forum Discussion
Teams build 25275.2601.4002.2815) instantly closes on launch ucrtbase.dll error 0xc0000409
After updating to Teams 25275.2601.4002.2815, the app opens for one second then closes—no UI, no error.
Env:
Win 11 Pro 23H2 (26100)
WebView2 141.0.3537.92
Entra ID joined (AAD)
Faulting module: ucrtbase.dll
Exception code: 0xc0000409
Path: C:\Program Files\WindowsApps\MSTeams_25275.2601.4002.2815_x64__8wekyb3d8bbwe\ms-teams.exe
Tried: cleared Teams/WebView2/AAD caches, reinstalled Teams + WebView2 + VC++, did Reset this PC and clean USB install — same result.
Works fine for local admin + other Entra users and browser.
Older builds (Aug/Sep 2025) work fine → likely regression in this release.
Please confirm if known and being investigated.
3 Replies
Thanks, support wasn't helpful as well, one tried to tell me that this is a windows problem and that i need premium support to fix it. Thing is, there is no option to roll back, i couldn't find a place to download an older version of "new teams"
Same problem, same version ....
This is a clear-cut case of a flawed Teams update.
Your diagnostic work is correct the crash points to a coding error in build 25275, not your PC.
Stop troubleshooting; the fault lies entirely with Microsoft's software.
Please report this via Feedback Hub with your details.
The only reliable fix is to uninstall this version and reinstall the older, working August/September build.
A rollback is your path to productivity until Microsoft provides a patch
