What is CVE-2026-6539?

CVE-2026-6539 is a medium-severity vulnerability in Notepad++, classified under Use of Externally-Controlled Format String. CVSS score: 4.4/10. Published 2026-04-30.

How severe is CVE-2026-6539?

Medium severity. CVSS v3 base score is 4.4 out of 10.

Vulnerability in Notepad++

CVE-2026-6539

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. Attac…

EPSS: 0.000 (0.7th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 4.4 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:L.

Affected products

Notepad++ — versions 0
Notepad-plus-plus Notepad\+\+ — versions 8.9.3

Weakness classification (CWE)

CWE-134 — Use of Externally-Controlled Format String

References

disclosure@vulncheck.com (Release Notes, patch)
disclosure@vulncheck.com (Third Party Advisory, third-party-advisory)

Frequently asked questions

What is CVE-2026-6539?: CVE-2026-6539 is a medium-severity vulnerability in Notepad++, classified under Use of Externally-Controlled Format String. CVSS score: 4.4/10. Published 2026-04-30.
How severe is CVE-2026-6539?: Medium severity. CVSS v3 base score is 4.4 out of 10.