# CVE-2026-6539: Notepad++ 8.9.3 Format String Injection via nativeLang.xml

CVE-2026-6539 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: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-6539
- Priority: Routine
- CVSS: 4.6
- EPSS: 0.0019
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Apr 30, 2026
- Weakness: CWE-134: Use of Externally Controlled Format String
- Vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-6539

## Description

Notepad++ 8.9.3 contains a format string injection vulnerability in the Find Results panel handler that allows attackers to cause denial of service and information disclosure by crafting a malicious nativeLang.xml language pack file. Attackers can distribute a poisoned language pack through community channels that triggers format string interpretation when a user performs search operations, leading to access violations and potential leakage of stack or register contents.

## 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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