# CVE-2026-54758: Notepad++ stack buffer overflow in expandNppEnvironmentStrs

Source: https://junglewise.ai/threats/cve-2026-54758-notepad-stack-buffer-overflow-in-expandnppenvironmentstrs  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-17. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-54758 · Severity: high · CVSS 7.8 · Published 2026-08-17

Notepad++ is a free source code editor used by millions of developers. A flaw in how it processes custom environment variable names allows an attacker to write excess data into memory, potentially crashing the application or executing malicious code on the developer's machine.

## Quick answers

**Is CVE-2026-54758 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-54758 being exploited in the wild.

**How severe is CVE-2026-54758?** High severity, with a CVSS score of 7.8, published 17 August 2026.

**Which products and versions are affected?** Notepad++ Team Notepad++ before 8.9.7.

**Is there a fix for CVE-2026-54758?** A patch was published on 2026-07-14: Fixed in version 8.9.7 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-54758 attacked?** It is attacked with local access.

**Am I affected by CVE-2026-54758?** 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

The expandNppEnvironmentStrs function in RunDlg.cpp contains a stack buffer overflow vulnerability. When parsing Notepad++ environment variables delimited by $( and ), the code copies the variable name into a fixed 260-character (MAX_PATH) wchar_t buffer without validating the loop index, allowing variable names longer than 260 characters to overflow adjacent stack memory. This can trigger a stack corruption guard (__report_gsfailure), crash the process, or permit arbitrary code execution. The vulnerability exists in all versions prior to 8.9.7 and is fixed by adding proper bounds checking to the loop.

## Affected products

- Notepad++ Team Notepad++ before 8.9.7

## Timeline

- 2026-08-17: disclosed
- 2026-07-14: patched: Fixed in version 8.9.7

## References

- [https://github.com/notepad-plus-plus/notepad-plus-plus/commit/0a9527e9f7140a2323e25d14e362b46ee0efc3db](https://github.com/notepad-plus-plus/notepad-plus-plus/commit/0a9527e9f7140a2323e25d14e362b46ee0efc3db)
- [https://github.com/notepad-plus-plus/notepad-plus-plus/releases/tag/v8.9.7](https://github.com/notepad-plus-plus/notepad-plus-plus/releases/tag/v8.9.7)