SibSoft Xfilesharing - Arbitrary File Upload (CVE-2019-18952)

CVE-2019-18952 is a critical vulnerability in SibSoft Xfilesharing up to version 2.5.1 that allows arbitrary file uploads via the cgi-bin/up.cgi endpoint. Attackers can exploit this flaw to upload malicious files, and when combined with CVE-2019-18951, it can lead to remote code execution by serving crafted .html files over HTTP. This vulnerability poses a severe risk, enabling threat actors to fully compromise affected systems.

CrowdSec has been tracking this vulnerability and its exploits since 15th of October 2025.

Data from the CrowdSec community indicates that exploitation of CVE-2019-18952 is highly selective and intelligence-driven. Threat actors use advanced reconnaissance and carefully choose their targets, often as part of sophisticated campaigns or advanced persistent threat operations. Data from the CrowdSec community also indicates a gradual decrease in attacks targeting CVE-2019-18952. While still present in the wild, exploitation levels have dropped noticeably week-over-week. This may signal that the vulnerability is becoming less relevant or that defenses are improving fast enough for attackers to lose interest.

Attackers exploit the /cgi-bin/up.cgi endpoint to upload arbitrary files, often with executable extensions, enabling remote code execution when the uploaded file is accessed via /cgi-bin/temp/.