CVE-2026-4744 is a critical security vulnerability classified as an out-of-bounds read (CWE-125) found in the rizonesoft Notepad3 text editor, specifically in versions prior to 6.25.714.1. The vulnerability resides in the regcomp.C source files within the scintilla and oniguruma modules, which are responsible for regular expression compilation and text processing. An out-of-bounds read occurs when the program reads memory beyond the allocated buffer, potentially exposing sensitive data or causing application crashes. The vulnerability can be triggered by a local attacker who can interact with the application, as it requires user interaction but does not require elevated privileges or authentication. The CVSS 4.0 vector indicates low attack complexity and no privileges required, but user interaction is necessary. The impact scope is high, affecting confidentiality, integrity, and availability, as the out-of-bounds read could lead to information disclosure or destabilize the application. Although no active exploits are reported, the high severity score (9.3) underscores the critical nature of this flaw. The vulnerability affects the core text processing components, making it relevant for users who open or process untrusted text inputs. Since Notepad3 is widely used as a lightweight editor on Windows platforms, the vulnerability poses a risk to many desktop environments. The lack of available patches at the time of reporting necessitates immediate attention from users and administrators to mitigate risks.

The primary impact of CVE-2026-4744 is the potential unauthorized disclosure of sensitive information due to out-of-bounds memory reads. This can compromise confidentiality by exposing data from adjacent memory areas. Additionally, the vulnerability can lead to application instability or crashes, affecting availability. Integrity could be indirectly impacted if the application behaves unpredictably or corrupts data during exploitation attempts. Since exploitation requires local access and user interaction, the threat is more significant in environments where multiple users share systems or where untrusted users have physical or remote desktop access. Organizations relying on Notepad3 for editing or processing text files could face data leakage risks or denial-of-service conditions. The vulnerability's presence in core text processing modules means that crafted inputs could be used to trigger the flaw, potentially as part of a broader attack chain. The high CVSS score reflects the severity and broad impact on confidentiality, integrity, and availability. Although no known exploits exist yet, the vulnerability is likely to attract attacker interest due to its critical nature.

1. Immediately update Notepad3 to version 6.25.714.1 or later once the patch is released by rizonesoft to address this vulnerability. 2. Until a patch is available, restrict local access to systems running Notepad3 to trusted users only, minimizing the risk of exploitation. 3. Educate users to avoid opening untrusted or suspicious text files in Notepad3, especially those received from unknown sources. 4. Employ application whitelisting and endpoint protection solutions to monitor and control the execution of Notepad3 and detect anomalous behavior. 5. Use operating system-level access controls to limit the ability of non-privileged users to run or interact with Notepad3 in sensitive environments. 6. Monitor system logs and user activity for unusual crashes or memory access errors related to Notepad3 that could indicate exploitation attempts. 7. Consider sandboxing or running Notepad3 in isolated environments when handling untrusted files to contain potential impacts. 8. Coordinate with IT and security teams to prioritize patch management and vulnerability scanning for desktop applications like Notepad3.