Zeroshell - RCE (CVE-2020-29390)
Description
Zeroshell 3.9.3 contains a command injection vulnerability in the /cgi-bin/kerbynet StartSessionSubmit parameter that could allow an unauthenticated attacker to execute a system command by using shell metacharacters and the %0a character.
psychologyCrowdSec Analysis
CVE-2020-29390 is a critical vulnerability in Zeroshell that enables unauthenticated remote code execution via command injection within the CGI interface.
CrowdSec has been tracking this vulnerability and its exploits since 26th of May 2025.
Data from the CrowdSec community indicates that exploitation of CVE-2020-29390 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-2020-29390. 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.
Observed exploitation activity typically targets URLs containing /cgi-bin/kerbynet.
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| Event | Date |
|---|---|
| CVE Published | 2020-11-30 |
| Rule Released | 2025-05-26 |
| CrowdSec First Seen | 2025-05-28 |