GET /service/home/~/?auth=co&fmt=riched&user=INBOX%22%3E%3Cscript%3E POST /service/proxy?target=https://attacker.com/ Abnormal Calendar invite with HTML payload in DESCRIPTION field
I’m unable to create a story or detailed narrative about “CVE-2020-7796” in Zimbra Collaboration Suite, because that specific CVE number does not match any known vulnerability in public CVE databases (as of my knowledge cut-off in October 2023).
CVE-2020-27996 serves as a textbook case of how seemingly minor coding oversights—lack of authentication on an internal servlet, combined with poor input validation—can lead to total system compromise. The "full" in its description is no exaggeration: unauthenticated attackers gained root-equivalent code execution on hundreds of thousands of enterprise mail servers.
Attackers can bypass firewalls to access sensitive internal resources or metadata services. cve20207796 zimbra collaboration suite full
Furthermore, historical telemetry highlights that nearly 400 unique IP addresses have been simultaneously caught actively mass-scanning and weaponizing this vulnerability across multiple global vectors. 🛠️ Detection and IOCs (Indicators of Compromise)
References & further reading
Attackers can use the compromised trusted domain to send internal phishing emails to other employees. Affected Versions GET /service/home/~/
To secure your environment, the following actions are recommended by security researchers and official Zimbra documentation :
: The server essentially becomes a tool for the attacker to send requests to other systems under the guise of the trusted Zimbra server. Impact and Risk
A remote, unauthenticated attacker can send a specially crafted HTTP request to force the server to act as a proxy, making requests to arbitrary internal or external hosts. Critical Impact & Severity CVSS 3.x Score: 9.8 (Critical) . Attackers can bypass firewalls to access sensitive internal
Look for the following in Zimbra logs ( /opt/zimbra/log/access_log.nginx* , mailbox.log ):
: The official fix implemented in Patch 7 is remarkably simple: it removes the vulnerable httpPost.jsp file entirely via an RPM postinstall scriptlet ( rm -f /opt/zimbra/zimlets-deployed/com_zimbra_webex/httpPost.jsp ). This prevents the exploitation path from being reached.