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CVE-2026-86056: Notepad++: Null pointer dereference in NPPM_SAVESESSION message handler causes crash (DoS)

• Severity: medium (CVSS 5.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-22 · updated 2026-09-23
• Weakness: CWE-476

Description

Notepad++ is a free and open-source source code editor. Prior to 8.9.8, the NPPM_SAVESESSION handler in PowerEditor/src/NppBigSwitch.cpp converts lParam to a sessionInfo pointer and dereferences its nbFile, files, and sessionFilePathName members without checking for null. A process running at the same or a higher Windows integrity level on the same desktop can send NPPM_SAVESESSION with a null lParam, immediately terminating Notepad++ and causing denial of service and loss of unsaved documents. This issue is fixed in version 8.9.8.

Affected products

• notepad-plus-plus: before 8.9.8

References

• https://github.com/notepad-plus-plus/notepad-plus-plus/commit/8b33f52e7aa488b1222d3cfce5903a38dd63101f
• https://github.com/notepad-plus-plus/notepad-plus-plus/releases/tag/v8.9.8
• https://github.com/notepad-plus-plus/notepad-plus-plus/security/advisories/GHSA-j85c-6wc9-p98p
• https://notepad-plus-plus.org/news/v898-released

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