Medium

Format String Injection in Notepad++ Find Results Panel

IdentifiersCVE-2026-6539CWE-134· Use of Externally-Controlled…

Notepad++ before 8.9.4 contains a format string injection vulnerability in the FindInFiles/Find Results handling path. According to the provided content, the issue is triggered when the nativeLang.xml language pack value for "find-result-hits" contains format specifiers such as "%s". When a user performs search operations, the application interprets attacker-controlled format tokens instead of treating them as literal text, causing crashes/access violations and potentially exposing process memory contents such as stack or register data. The issue was fixed in Notepad++ 8.9.4 and is associated with the patch referenced by issue #17960.

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ANALYST BRIEF

Impact, mitigation & remediation

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Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation can cause denial of service by crashing Notepad++ during search operations. The format string condition may also disclose sensitive process memory contents, including stack or register-derived data or memory addresses, which could aid further exploitation such as bypassing mitigations like ASLR. Based on the provided content, the primary demonstrated impacts are application instability/crash and information disclosure rather than direct code execution.

Mitigation

If you can’t patch tonight, do this now.

If immediate patching is not possible, avoid using untrusted or community-sourced nativeLang.xml language pack files and review existing custom localization files for format specifiers in the "find-result-hits" field. Restrict deployment of third-party language packs to trusted, validated sources, and monitor for abnormal Notepad++ crashes during search operations that could indicate attempted exploitation. Prioritize patching systems where custom nativeLang.xml configurations are used.

Remediation

Patch, then assume compromise.

Upgrade Notepad++ to version 8.9.4 or later. The provided content states that version 8.9.4 specifically fixes the FindInFiles crash related to nativeLang.xml "find-result-hits" containing "%s" and addresses CVE-2026-6539. Obtain the update from the official Notepad++ distribution channel or built-in updater and verify installer integrity using the project's published signatures and SHA-256 digests.

PUBLIC EXPLOITS

Exploits

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VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

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VendorProductType

Notepad++Notepad Plus Plusapplication

Notepad++Notepad++application

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ACTIVITY FEED

Recent activity

5 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

5 SOURCESView more in app

cyber security newsNews

Apr 27, 2026

Notepad++ Vulnerability Allows Attackers to Crash Application, Leak Memory Data

An additional Notepad++ vulnerability referenced as being fixed in the same 8.9.4 patch, though technical details are not provided in the content.

notepad plus plusNews

Apr 26, 2026

Download Notepad++ v8.9.4 | Notepad++

A vulnerability associated with a crash in Notepad++ FindInFiles when nativeLang.xml's "find-result-hits" contains "%s".

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