CVE-2023-40166Public exploit

Process-memory read via unchecked language-detection copy

Published Aug 25, 2023 · Updated Oct 2, 2024

Heap buffer over-read in Notepad++ 8.5.6 and earlier allows context-dependent attackers to expose process memory via a crafted file. FileManager::detectLanguageFromTextBegining skips whitespace to the input length, then copies 40 bytes without limiting the copy to the remaining buffer. A user must open an all-whitespace file; the proof of concept causes a memory-read exception, and no memory-disclosure exploit is demonstrated.

CVSS severity5.5
Medium
EPSS probability0.41%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap buffer over-read in Notepad++ 8.5.6 and earlier allows context-dependent attackers to expose process memory via a crafted file. FileManager::detectLanguageFromTextBegining skips whitespace to the input length, then copies 40 bytes without limiting the copy to the remaining buffer. A user must open an all-whitespace file; the proof of concept causes a memory-read exception, and no memory-disclosure exploit is demonstrated.

The record

CVE
CVE-2023-40166
Published
Aug 25, 2023
Updated
Oct 2, 2024
Vendor
Notepad++
Product
Notepad++
Classifications
CWE-125, T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 25, 2023CVE publishedPublication date reported by the CVE source.
  2. Oct 2, 2024Record 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=<= 8.5.6

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Notepad++ · Notepad++version=<= 8.5.6

Published CVSS scores

5.5GitHub, Inc.CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A: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-125Out-of-bounds Read
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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