Notepad++: Stack Buffer Overflow in `NppParameters::writeSession` via overlong session path
CVE-2026-86054 is fixed in Notepad++ on 1 platform by Notepad++ 8.9.8 (version 8.9.8), released August 23, 2026. It is not reported as exploited. Patch Radar priority: High.
Notepad++ is a free and open-source source code editor. Prior to 8.9.8, Notepad++ contains a stack buffer overflow in NppParameters::writeSession in PowerEditor/src/Parameters.cpp because it copies a session path derived from -settingsDir= into backupPathName[MAX_PATH] with unbounded wcscpy and appends SESSION_BACKUP_EXT with unbounded wcscat. A sufficiently long settings directory causes the backup suffix to exceed the fixed stack buffer when Notepad++ saves the session, and the protected release build terminates through its stack canary, causing denial of service. This issue is fixed in version 8.9.8.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Windows apps | |||
| Notepad++ | 8.9.8 | Notepad++ 8.9.8 | Aug 23, 2026 |
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