# CVE-2026-48770: Notepad++ out-of-bounds read in WM_COPYDATA handler

Source: https://junglewise.ai/threats/cve-2026-48770-notepad-out-of-bounds-read-in-wm-copydata-handler  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-26. Updated: 2026-06-26  
License: CC BY 4.0 with a link back

CVE-2026-48770 · Severity: medium · CVSS 5 · Published 2026-06-26

Notepad++ is a popular open-source text and source code editor for Windows. A vulnerability in how the application handles internal communication messages allows other programs running on the same computer to force Notepad++ to crash. This results in a denial-of-service where a user may lose unsaved work if a malicious or malfunctioning local process triggers the flaw.

## Quick answers

**Is CVE-2026-48770 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-48770 being exploited in the wild.

**How severe is CVE-2026-48770?** Medium severity, with a CVSS score of 5, published 26 June 2026.

**Which products and versions are affected?** Notepad++ Notepad++ < 8.9.6.1.

**Is there a fix for CVE-2026-48770?** A patch was published on 2026-06-26: Fix included in version 8.9.6.1 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-48770 attacked?** It is attacked with local access, in a network appliance.

**Am I affected by CVE-2026-48770?** Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

An out-of-bounds read vulnerability (CWE-125) exists in Notepad++ prior to version 8.9.6.1. The issue resides in the handling of 'WM_COPYDATA' messages, specifically within the 'COPYDATA_FULL_CMDLINE' path in 'NppBigSwitch.cpp'. The application processes 'COPYDATASTRUCT.lpData' as an unbounded, NUL-terminated 'wchar_t*' string without validating the 'cbData' length field. By sending a malformed message with a large 'cbData' value and a buffer lacking a NUL terminator, a local process in the same interactive session can trigger an access violation (0xc0000005). This results in a reliable application crash. The vulnerability is fixed in version 8.9.6.1 by implementing proper bounds checking and exception handling during command-line string processing.

## Affected products

- Notepad++ Notepad++ < 8.9.6.1

## Timeline

- 2026-05-26: advisory: GitHub Security Advisory published by vendor
- 2026-06-26: disclosed: CVE published to NVD
- 2026-06-26: patched: Fix included in version 8.9.6.1

## References

- [https://github.com/notepad-plus-plus/notepad-plus-plus/commit/f20a0888a92ce557a339b833cd9d9d8e97dc797d](https://github.com/notepad-plus-plus/notepad-plus-plus/commit/f20a0888a92ce557a339b833cd9d9d8e97dc797d)
- [https://github.com/notepad-plus-plus/notepad-plus-plus/security/advisories/GHSA-r39g-3mcw-xcg2](https://github.com/notepad-plus-plus/notepad-plus-plus/security/advisories/GHSA-r39g-3mcw-xcg2)