CVE-2025-15556 in Notepad++
Summary
by MITRE • 02/03/2026
Notepad++ versions prior to 8.8.9, when using the WinGUp updater, contain an update integrity verification vulnerability where downloaded update metadata and installers are not cryptographically verified. An attacker able to intercept or redirect update traffic can cause the updater to download and execute an attacker-controlled installer, resulting in arbitrary code execution with the privileges of the user.
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Analysis
by VulDB Data Team • 03/20/2026
The vulnerability identified as CVE-2025-15556 affects Notepad++ versions prior to 8.8.9 and specifically targets the WinGUp updater component used for software updates. This represents a critical security flaw that undermines the integrity of the software update mechanism, creating a pathway for malicious actors to compromise user systems through supply chain attacks. The vulnerability stems from insufficient cryptographic verification processes that should validate the authenticity and integrity of update metadata and installer files before execution.
The technical implementation flaw resides in the WinGUp updater's failure to perform proper digital signature verification or cryptographic checksum validation of downloaded update components. This weakness allows an attacker positioned within the network traffic path to perform man-in-the-middle attacks or DNS hijacking to redirect update requests to malicious servers. When users attempt to update Notepad++, the updater downloads both metadata files and executable installers without validating their cryptographic integrity, creating a window of opportunity for attackers to substitute legitimate update files with malicious payloads that appear legitimate to the system.
The operational impact of this vulnerability extends beyond simple code execution privileges, as it enables attackers to escalate their compromise through the software update process. Since the updater operates with the privileges of the user who initiated the update, successful exploitation results in arbitrary code execution within the user context, potentially leading to full system compromise if users have administrative privileges. This vulnerability particularly affects environments where network traffic interception is feasible, making it a significant concern for enterprise networks, public Wi-Fi environments, and any scenario where update traffic might be subject to network-level attacks.
Organizations and users should immediately upgrade to Notepad++ version 8.8.9 or later to remediate this vulnerability, as the fix implements proper cryptographic verification of update metadata and installers. System administrators should also consider implementing network-level protections such as DNS filtering and network monitoring to detect potential update traffic redirection attempts. The vulnerability aligns with CWE-347, which addresses improper verification of cryptographic signatures, and maps to ATT&CK technique T1068, which covers exploit for privilege escalation through legitimate system tools. Additional mitigations include configuring firewall rules to restrict outbound update traffic to trusted repositories and implementing network segmentation to limit the attack surface for potential interception attempts.