CVE-2019-25628: Download Accelerator Plus Buffer Overflow

CVE-2019-25628 Overview

Download Accelerator Plus (DAP) version 10.0.6.0 contains a critical structured exception handler (SEH) buffer overflow vulnerability that allows remote attackers to execute arbitrary code. The vulnerability exists in the application's web page import functionality, where specially crafted URLs can trigger a buffer overflow condition that overwrites SEH pointers. When successfully exploited, attackers can redirect program execution flow to embedded shellcode, resulting in arbitrary code execution on the target system.

Critical Impact

Remote attackers can achieve arbitrary code execution by crafting malicious URLs that exploit the SEH buffer overflow in DAP's import functionality, potentially leading to complete system compromise.

Affected Products

• Download Accelerator Plus (DAP) 10.0.6.0
• SpeedBit Download Accelerator Plus

Discovery Timeline

• 2026-03-24 - CVE-2019-25628 published to NVD
• 2026-03-24 - Last updated in NVD database

Technical Details for CVE-2019-25628

Vulnerability Analysis

This vulnerability is classified as CWE-787 (Out-of-Bounds Write), a memory corruption flaw that occurs when the application writes data past the allocated buffer boundaries. The SEH buffer overflow in Download Accelerator Plus occurs during the processing of URLs imported through the application's web page import feature. When a user imports a maliciously crafted URL containing excessive data, the application fails to properly validate the input length before copying it to a fixed-size buffer on the stack.

The overflow condition allows attackers to overwrite the Structured Exception Handler (SEH) chain stored on the stack. SEH is a Windows mechanism for handling exceptions, and by corrupting these pointers, attackers can hijack the exception handling process. When an exception is triggered (often deliberately as part of the exploit), the corrupted SEH pointer redirects execution to attacker-controlled shellcode embedded within the malicious URL payload.

Root Cause

The root cause of this vulnerability is insufficient input validation and improper boundary checking when processing URL data in the web page import functionality. The application allocates a fixed-size buffer for URL storage but does not verify that incoming URL data fits within the allocated space. This allows oversized input to overflow the buffer and corrupt adjacent memory structures, including the SEH chain.

Attack Vector

The attack vector is network-based, requiring an attacker to deliver a specially crafted URL to a victim. This can be accomplished through various social engineering techniques, such as embedding malicious URLs in web pages, emails, or documents that the victim might import into Download Accelerator Plus. When the victim uses the application's import feature to process the malicious URL, the buffer overflow triggers and executes the attacker's shellcode with the privileges of the DAP process.

The exploitation chain typically follows this sequence: the attacker crafts a URL containing padding data to reach the SEH overwrite offset, a pointer to a POP-POP-RET gadget that passes control to the next SEH handler, and the embedded shellcode payload. Once the buffer overflow corrupts the SEH chain and an exception occurs, Windows invokes the corrupted handler, ultimately transferring execution to the malicious payload.

For detailed technical analysis and proof-of-concept information, refer to the Exploit-DB entry #46673 and the VulnCheck Advisory.

Detection Methods for CVE-2019-25628

Indicators of Compromise

• Unusual crash logs or exceptions within the dap.exe process indicating SEH corruption
• Presence of unusually long URLs in DAP import logs or temporary files
• Unexpected child processes spawned by Download Accelerator Plus
• Network connections initiated by DAP to suspicious or unknown IP addresses

Detection Strategies

• Deploy endpoint detection and response (EDR) solutions to monitor for SEH exploitation patterns in the DAP process
• Implement application control policies to restrict or monitor Download Accelerator Plus usage
• Monitor for process injection or unusual code execution behavior originating from dap.exe
• Configure intrusion detection systems to flag extremely long URL patterns in network traffic

Monitoring Recommendations

• Enable detailed logging for Download Accelerator Plus application activity
• Monitor Windows Event Logs for application crashes and exception events related to DAP
• Implement file integrity monitoring on DAP installation directories
• Track outbound network connections from the DAP process for anomalous destinations

How to Mitigate CVE-2019-25628

Immediate Actions Required

• Consider removing or disabling Download Accelerator Plus 10.0.6.0 from enterprise environments until a patch is available
• Implement application whitelisting to prevent unauthorized execution of vulnerable software
• Educate users about the risks of importing URLs from untrusted sources
• Deploy network-level filtering to block known malicious URL patterns targeting this vulnerability

Patch Information

No official vendor patch information is currently available for this vulnerability. Users are advised to check the SpeedBit Download Accelerator website for the latest version updates and security advisories. If an updated version is available, upgrade immediately to address this vulnerability.

Workarounds

• Avoid using the web page import functionality with untrusted or unknown URL sources
• Run Download Accelerator Plus in a sandboxed environment or virtual machine to contain potential exploitation
• Implement strict network segmentation to limit the impact of potential compromise
• Use alternative download manager applications that are actively maintained and regularly patched

# Example: Blocking DAP execution via Windows AppLocker policy
# Create a rule to block dap.exe execution until patched
# Open Local Group Policy Editor and navigate to:
# Computer Configuration > Windows Settings > Security Settings > Application Control Policies > AppLocker
# Create a new executable rule to deny execution of:
# Path: %PROGRAMFILES%\DAP\dap.exe
# Publisher: SpeedBit Ltd