CVE-2026-86054: Notepad-Plus-Plus

High severity, CVSS 7.8. EPSS: 0.2% chance of exploitation in the next 30 days.

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.

Affected products

• Notepad-Plus-Plus Notepad-Plus-Plus: before 8.9.8 (fixed in 8.9.8)

Published 2026-09-22. Last modified 2026-09-28.