# CVE-2026-6539: Notepad++ 8.9.3 Format String Injection via nativeLang.xml

> Attackers can cause denial of service and information disclosure in Notepad++ by distributing a malicious language pack file.

- **Severity:** Medium 4.6 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:L/VI:N/VA:L/SC:N/SI:N/SA: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:** 30 Apr 2026
- **Updated:** 28 Jul 2026
- **Also known as:** GHSA-vfqp-r766-g759

## What is CVE-2026-6539?

CVE-2026-6539 is a medium-severity vulnerability in Notepad++, published on 30 Apr 2026. 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++ 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. Attackers can distribute a poisoned language pack through community channels that triggers format string interpretation when a user performs search operations, leading to access violations and potential leakage of stack or register contents.

Weakness: CWE-134 (Use of Externally-Controlled Format String)

## Which versions are affected by CVE-2026-6539?

It affects 1 product.


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

## How do I fix CVE-2026-6539?

No fix has been published for CVE-2026-6539 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-6539 being exploited?

There is no known exploitation of CVE-2026-6539 in the wild and no public exploit code.

## Other vulnerabilities in Notepad++

- [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-2026-6539 and fix it if it is affected.

What it is: CVE-2026-6539 is a medium-severity vulnerability in Notepad++, published on 30 Apr 2026. 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: There is no known exploitation of CVE-2026-6539 in the wild and no public exploit code.

Affected product: Notepad++. 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-2026-6539/ (Markdown: https://insights.sbomify.com/CVE-2026-6539/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-6539
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-6539
- OSV: https://osv.dev/vulnerability/CVE-2026-6539

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-6539/
Summaries are generated and may contain mistakes; the official description above is the record.