# CVE-2026-5525: Stack-Based Buffer Overflow in Notepad++ File Drop Handler leads to DoS

CVE-2026-5525 is fixed in Notepad++ on 1 platform by Notepad++ 8.9.4 (version 8.9.4), released April 26, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-5525
- Priority: High
- CVSS: 7.8
- EPSS: 0.0017
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Apr 10, 2026
- Weakness: CWE-121: Stack-based Buffer Overflow
- Vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-5525

## Description

A stack-based buffer overflow vulnerability exists in Notepad++ version 8.9.3 in the file drop handler component. When a user drags and drops a directory path of exactly 259 characters without a trailing backslash, the application appends a backslash and null terminator without proper bounds checking, resulting in a stack buffer overflow and application crash (STATUS_STACK_BUFFER_OVERRUN).

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Windows apps | Notepad++ | 8.9.4 | [Notepad++ 8.9.4](https://patchblox.com/security/data/fix/windows-app/notepad-.notepad-8.9.4.md) | Apr 26, 2026 |

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Data as of 2026-11-08T06:59:42Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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