# CVE-2026-86054: 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.

- Web page: https://patchblox.com/security/cve/CVE-2026-86054
- Priority: High
- CVSS: 7.8
- EPSS: 0.0023
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 22, 2026
- Weakness: CWE-121: Stack-based Buffer Overflow
- Vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-86054

## Description

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

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Windows apps | Notepad++ | 8.9.8 | [Notepad++ 8.9.8](https://patchblox.com/security/data/fix/windows-app/notepad-.notepad-8.9.8.md) | Aug 23, 2026 |

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Data as of 2026-11-09T07:25:28Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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