Notepad++: Stack Buffer Overflow in `NppParameters::writeSession` via overlong session path (CVE-2026-86054) | HOL Guard CVE

High · CVSS 7.8CVE-2026-86054

Notepad++: Stack Buffer Overflow in `NppParameters::writeSession` via overlong session path

Answer in brief

CVE-2026-86054 records a High severity (CVSS 7.8) vulnerability in Notepad++: Stack Buffer Overflow in `NppParameters::writeSession` via overlong session path. The current sources do not mark it as known exploited. The current feed maps notepad-plus-plus/notepad-plus-plus (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 22, 2026Updated Sep 22, 2026Source checked Sep 22, 2026First seen by HOL Sep 22, 2026Material review Sep 22, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 7.8
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 7.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps notepad-plus-plus/notepad-plus-plus (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
notepad-plus-plus/notepad-plus-plusgeneric	<8.9.8	8.9.8

Recommended response

Check inventory. Check lockfiles and deployed manifests for notepad-plus-plus/notepad-plus-plus.
Review the reported fix. Update notepad-plus-plus/notepad-plus-plus to 8.9.8 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 22, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 22, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 22, 2026

Sources and claim methodology

Upstream source description

Notepad++ is a free and open-source source code editor. Prior to 8.9.8, Notepad++ contains a stack buffer overflow in NppParameters::writeSession in PowerEditor/src/Parameters.cpp because it copies a session path derived from -settingsDir= into backupPathName[MAX_PATH] with unbounded wcscpy and appends SESSION_BACKUP_EXT with unbounded wcscat. A sufficiently long settings directory causes the backup suffix to exceed the fixed stack buffer when Notepad++ saves the session, and the protected release build terminates through its stack canary, causing denial of service. This issue is fixed in version 8.9.8.

Quoted source text, attributed separately from HOL analysis.