Executive Summary

This vulnerability is a lack of rate limiting in the /Home/UploadStreamDocument component of SigningHub version 8.6.8 and earlier. It allows attackers to upload an excessive number of files without restriction, which can overwhelm the system. [2]

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Impact Analysis

The vulnerability can lead to a Denial of Service (DoS) by exhausting system resources such as disk space and increasing server load. This results in degraded system performance or complete unavailability of the SigningHub service. [2]

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Detection Guidance

This vulnerability can be detected by monitoring for an unusually high number of file upload requests to the /Home/UploadStreamDocument API endpoint. Network or system logs showing rapid, repeated uploads from the same source may indicate exploitation attempts. Commands to detect this could include using web server access logs analysis, for example: 1) Using grep to filter upload requests: grep "/Home/UploadStreamDocument" /var/log/nginx/access.log 2) Counting requests per IP: grep "/Home/UploadStreamDocument" /var/log/nginx/access.log | awk '{print $1}' | sort | uniq -c | sort -nr 3) Using network monitoring tools like tcpdump or Wireshark to capture traffic to the affected endpoint. Specific commands depend on your environment and logging setup. [2]

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Mitigation Strategies

Immediate mitigation steps include implementing rate limiting or throttling on the /Home/UploadStreamDocument API to restrict the number of file uploads per user or IP address. Additionally, upgrading SigningHub to a version later than 8.6.8 where the vulnerability is fixed is recommended. Monitoring and alerting on unusual upload activity can also help mitigate potential exploitation. [2]

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