# CVE-2023-40166: Notepad++ heap buffer read overflow in FileManager::detectLanguageFromTextBegining

> A heap buffer read overflow in Notepad++ may allow attackers to leak internal memory allocation information.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 25 Aug 2023
- **Updated:** 2 Oct 2024

## What is CVE-2023-40166?

CVE-2023-40166 is a medium-severity memory corruption vulnerability in notepad-plus-plus, published on 25 Aug 2023. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

Notepad++ is a free and open-source source code editor. Versions 8.5.6 and prior are vulnerable to heap buffer read overflow in `FileManager::detectLanguageFromTextBegining `. The exploitability of this issue is not clear. Potentially, it may be used to leak internal memory allocation information. As of time of publication, no known patches are available in existing versions of Notepad++.

Weakness: CWE-122 (Heap-based Buffer Overflow), CWE-120 (Buffer Copy without Checking Size of Input)

## Which versions are affected by CVE-2023-40166?

It affects 1 product.


Products: Notepad-Plus-Plus Notepad\+\+.

## How do I fix CVE-2023-40166?

No fix has been published for CVE-2023-40166 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-40166 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-40166 exists.

## Other vulnerabilities in notepad-plus-plus

- [CVE-2025-15556](https://insights.sbomify.com/CVE-2025-15556/): Notepad++ Download of Code Without Integrity Check (high 7.7, exploited in the wild)
- [CVE-2026-48778](https://insights.sbomify.com/CVE-2026-48778/): Notepad++: Arbitrary Code Execution via config.xml commandLineInterpreter (high 7.8)
- [CVE-2026-48800](https://insights.sbomify.com/CVE-2026-48800/): Notepad++: Arbitrary Code Execution via shortcuts.xml UserCommand Injection (high 7.8)
- [CVE-2026-52884](https://insights.sbomify.com/CVE-2026-52884/): Notepad++: CVE-2026-48800 Bypass (high 7.8)
- [CVE-2023-47452](https://insights.sbomify.com/CVE-2023-47452/): Privilege escalation in n/a (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-40166 and fix it if it is affected.

What it is: CVE-2023-40166 is a medium-severity memory corruption vulnerability in notepad-plus-plus, published on 25 Aug 2023. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-40166 exists.

Affected product: notepad-plus-plus. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2023-40166/ (Markdown: https://insights.sbomify.com/CVE-2023-40166/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-40166
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-40166
- OSV: https://osv.dev/vulnerability/CVE-2023-40166

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-40166/
Summaries are generated and may contain mistakes; the official description above is the record.