CVE-2026-121451 in AB Download Manager
Summary
by MITRE • 11/03/2026
AB Download Manager before 1.11.2 contains a cross-site request forgery vulnerability in its unauthenticated browser-integration API that allows remote attackers to write attacker-chosen files to arbitrary paths. A malicious web page can send a text/plain request to /start-headless-download with crafted folder and name values, placing payloads in startup folders for code execution on next login.
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Analysis
by VulDB Data Team • 11/03/2026
The vulnerability identified in AB Download Manager prior to version 1.11.2 represents a critical security flaw rooted in the application's unauthenticated browser-integration API. This specific weakness allows remote attackers to perform cross-site request forgery attacks against users who have the software installed and potentially active browser extensions or integrations enabled. The core of the issue lies in the lack of proper authentication checks for certain endpoints, specifically the /start-headless-download endpoint. Because this interface does not verify that incoming requests originate from a legitimate user session or contain valid anti-CSRF tokens, it can be exploited by malicious web pages to execute actions on behalf of authenticated users without their knowledge or consent. This architectural oversight transforms what should be a controlled download management feature into an attack vector for arbitrary file system manipulation and potential remote code execution.
The technical mechanism of the exploit involves crafting specific HTTP requests with content type text/plain that target the vulnerable endpoint. By manipulating parameters such as folder path and filename, an attacker can dictate where downloaded files are saved on the victim's local machine. The severity of this vulnerability is significantly amplified by the ability to write files to arbitrary paths rather than being restricted to a designated downloads directory. Attackers leverage this capability to place malicious payloads directly into system startup folders or other directories that are automatically executed during the operating system initialization process. This technique bypasses many traditional security controls because it relies on legitimate application behavior—downloading and saving files—to achieve persistence, making detection by standard antivirus solutions more difficult unless they specifically monitor for suspicious file placements in critical system locations.
The operational impact of this vulnerability is severe, as it facilitates a chain of events leading to remote code execution with the privileges of the currently logged-in user. Once a malicious web page triggers the forged request, AB Download Manager saves the attacker-controlled payload into a startup directory. When the victim logs out and subsequently logs back in, or when the system restarts depending on the specific path targeted, the operating system executes the injected file. This results in the arbitrary execution of code chosen by the remote attacker, potentially leading to full compromise of the user's account, theft of sensitive data, installation of additional malware such as ransomware or keyloggers, and establishment of a persistent foothold within the network environment. The attack requires no special privileges for the initial exploitation but relies on social engineering or drive-by download tactics to get the victim to visit the malicious webpage while AB Download Manager is running in the background with its browser integration active.
From an industry standards perspective, this vulnerability aligns closely with CWE-352 Cross-Site Request Forgery (CSRF), as it involves tricking a user into performing unwanted actions via forged requests from another site. Furthermore, the technique of writing files to startup folders for persistence and execution maps directly to ATT&CK techniques such as T1059 Command and Scripting Interpreter if scripts are used, or more broadly to Persistence mechanisms like T1547 Boot or Logon Autostart Execution. The ability to write arbitrary files also touches upon CWE-22 Path Traversal concepts in the context of destination control, although it is primarily an abuse of functionality rather than a traversal attack per se. These mappings highlight that while the entry point is CSRF, the ultimate goal and method involve sophisticated persistence strategies commonly seen in advanced persistent threat campaigns.
Mitigation for this vulnerability requires immediate action by users to upgrade AB Download Manager to version 1.11.2 or later, where these authentication checks have presumably been implemented to prevent unauthenticated access to critical API endpoints. In addition to software updates, system administrators and security teams should enforce strict browser policies that restrict the capabilities of downloaded files, particularly preventing execution from startup directories unless explicitly whitelisted by group policy. Monitoring for unusual file creation events in sensitive paths such as AppData or ProgramData startup folders can also aid in early detection of exploitation attempts. Users are advised to disable unnecessary browser integrations within download managers and maintain up-to-date endpoint protection solutions that monitor for behavioral anomalies indicative of persistence mechanism deployment, thereby reducing the attack surface available to adversaries exploiting this specific flaw.