Cve20207796 Zimbra Collaboration Suite Full

CVE-2020-7796 is a critical security vulnerability affecting the Zimbra Collaboration Suite (ZCS). The flaw allows an unauthenticated, remote attacker to execute arbitrary code on the affected server. This vulnerability arises from improper input sanitization in the unrar binary utility used by the Amavis spam/antivirus scanning service.

Because the vulnerability allows for unauthenticated Remote Code Execution (RCE) with root privileges, it poses a severe risk to organizational security. Successful exploitation grants the attacker full control over the email server, potentially leading to data theft, email interception, ransomware deployment, or lateral movement within the network.

The attacker first checks if the target Zimbra server is vulnerable by sending a benign request to the proxy endpoint and examining the response headers or error messages. cve20207796 zimbra collaboration suite full

The impact of this vulnerability is severe and multifaceted:

The exploitation of this vulnerability is relatively straightforward, making it a prime target for threat actors. The attack chain typically proceeds as follows: The servlet is supposed to restrict paths to

Zimbra allows extensions and custom handlers via Java servlets. One such servlet is the UserServlet (or ProxyServlet), which is designed to fetch resources on behalf of a user. This servlet accepts parameters that specify the target URL or resource path.

The flaw resides in how the servlet validates (or fails to validate) the file parameter. In a typical request: due to insufficient sanitization

https://zimbra.example.com/proxy?file=/some/localfile.txt

The servlet is supposed to restrict paths to within the Zimbra installation directory. However, due to insufficient sanitization, an attacker could supply a path with directory traversal (../) or inject command delimiters.