CVE-2026-6539Public exploit

Crash and memory disclosure via localization format string

Published Apr 30, 2026 · Updated Apr 30, 2026

Format string injection in Notepad++ before 8.9.4 allows attackers to crash the editor or disclose process memory via nativeLang.xml. The Find Results handler treats the find-result-hits localization value as a format string, so %s crashes and %x or %08lx exposes register or stack values when search results render. Exploitation requires a crafted language pack to replace nativeLang.xml and user interaction to run a search; impact is limited to editor availability and process-memory disclosure.

CVSS severity4.6
Medium
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Format string injection in Notepad++ before 8.9.4 allows attackers to crash the editor or disclose process memory via nativeLang.xml. The Find Results handler treats the find-result-hits localization value as a format string, so %s crashes and %x or %08lx exposes register or stack values when search results render. Exploitation requires a crafted language pack to replace nativeLang.xml and user interaction to run a search; impact is limited to editor availability and process-memory disclosure.

The record

CVE
CVE-2026-6539
Published
Apr 30, 2026
Updated
Apr 30, 2026
Vendor
Notepad++
Product
Notepad++
Classifications
CWE-134, T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 30, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 30, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <8.9.4

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Notepad++ · Notepad++version=0 <8.9.4

Published CVSS scores

4.4VulnCheckCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:L
4.6VulnCheckCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-134Use of Externally-Controlled Format String
T1204.002Malicious File

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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