CVE-2024-45519
Synacor Zimbra Collaboration Suite (ZCS) Command Execution Vulnerability
Description
CVE-2024-45519 is a critical unauthenticated remote code execution vulnerability in the postjournal service of Zimbra Collaboration Suite (ZCS), the widely deployed open-source email and collaboration platform. An attacker can exploit this flaw without any authentication to execute arbitrary operating system commands on the Zimbra server, achieving complete system compromise. With the maximum possible CVSS v3.1 base score of 10.0 and a changed scope that extends impact beyond the vulnerable component, the vulnerability affects ZCS versions before 8.8.15 Patch 46, 9.0.0 Patch 41, 10.0.9, and 10.1.1. CISA has added CVE-2024-45519 to the Known Exploited Vulnerabilities catalog with a remediation deadline of October 24, 2024, and the extraordinary EPSS score of 94.11% at the 99.9th percentile confirms this is among the most actively exploited vulnerabilities globally.
KEV Information
CVSS Score
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:HOpen in CalculatorAffected Products
| Vendor | Product | Version |
|---|---|---|
| synacor | zimbra collaboration suite | < 8.8.15; >= 10.0.0, < 10.0.9; 8.8.15; 9.0.0; 10.1.0 |
Multiple CVSS Assessments
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
References
- https://wiki.zimbra.com/wiki/Security_Center(Release Notes)
- https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.9#Security_Fixes(Release Notes)
- https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.1#Security_Fixes(Release Notes)
- https://wiki.zimbra.com/wiki/Zimbra_Releases/8.8.15/P46#Security_Fixes(Release Notes)
- https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P41#Security_Fixes(Release Notes)
- https://wiki.zimbra.com/wiki/Zimbra_Responsible_Disclosure_Policy(Not Applicable)
- https://blog.projectdiscovery.io/zimbra-remote-code-execution/(Exploit)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-45519(US Government Resource)
Weakness Type
Unauthenticated Command Injection in postjournal Service
CVE-2024-45519 is an unauthenticated command injection vulnerability in Zimbra Collaboration Suite's postjournal service. The postjournal service is responsible for processing email journal messages and is exposed to the network as part of Zimbra's mail processing pipeline. The vulnerability exists because the service fails to properly sanitize user-controlled input before passing it to operating system command execution functions. An attacker can craft specially formatted email messages or direct requests to the postjournal service endpoint that inject arbitrary shell commands, which are then executed by the server with the privileges of the Zimbra service account. This represents a classic command injection pattern where untrusted external input reaches a system command execution interface without adequate validation or sanitization.
Impact Analysis
Confidentiality is fully compromised by CVE-2024-45519, and the changed scope (S:C) means the impact extends beyond the vulnerable postjournal service to affect the entire hosting environment. An attacker achieving remote code execution on a Zimbra server gains access to all email data for every user account hosted on that server, including attachments, calendar entries, contacts, and archived communications. Zimbra servers frequently store years of organizational communication history, making this an extraordinarily valuable target for espionage and data exfiltration.
Integrity faces maximum impact as the attacker can modify email content, inject messages, alter server configurations, install persistent backdoors, and manipulate the entire collaboration platform. The changed scope means the attacker can pivot from the Zimbra service to attack the underlying operating system and any other services running on the same infrastructure. The ability to forge or modify emails is particularly dangerous for organizations that rely on Zimbra for official communications.
Availability is completely compromised since the attacker can shut down the mail server, encrypt or delete all email data, deploy destructive payloads, or use the compromised server as a launching point for further attacks. The EPSS score of 94.11% at the 99.9th percentile is among the highest possible, indicating massive global exploitation. While ransomware association is listed as unknown, Zimbra servers represent ideal ransomware targets due to the critical nature of email data and the immediate operational impact of email service disruption on organizations.
Exploit Maturity
CVE-2024-45519 demonstrates the highest possible level of exploit maturity with widespread active exploitation confirmed across the internet. Its inclusion in CISA's Known Exploited Vulnerabilities catalog with a deadline of October 24, 2024, and an extraordinary EPSS score of 94.11% at the 99.9th percentile places it among the most exploited vulnerabilities in existence.
A detailed technical analysis and proof-of-concept exploit has been published by Project Discovery, providing a comprehensive walkthrough of the exploitation technique. This public exploit significantly lowered the barrier to entry for attackers. Zimbra has released patches across all supported version branches, documented in their Security Center with specific fix details available for versions 10.0.9, 10.1.1, 8.8.15 Patch 46, and 9.0.0 Patch 41. The unauthenticated nature of the vulnerability (PR:N), combined with no user interaction required (UI:N), network accessibility (AV:N), and the availability of public exploits, makes this trivially exploitable by attackers of all skill levels. Mass scanning campaigns targeting vulnerable Zimbra instances were detected within days of the public exploit release.
Remediation
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Patch Zimbra Collaboration Suite immediately. Update to ZCS 8.8.15 Patch 46, 9.0.0 Patch 41, 10.0.9, or 10.1.1 or later, depending on your installed version branch. Refer to the Zimbra Security Center for version-specific upgrade instructions. Given the critical severity and active mass exploitation, this patch should be treated as an emergency update.
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Disable or restrict access to the postjournal service. If the postjournal journaling feature is not required in your environment, disable it entirely. If it must remain active, restrict network access to the postjournal service port using firewall rules, limiting connectivity to only trusted mail relay servers.
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Conduct immediate forensic investigation. Any internet-facing Zimbra server running a vulnerable version should be assumed compromised until proven otherwise. Examine system logs, cron jobs, web shells in the Zimbra webroot, unauthorized SSH keys, and unusual network connections. Check for indicators of compromise associated with known exploitation campaigns targeting CVE-2024-45519.
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Rotate all credentials and secrets. After patching, change all Zimbra administrative passwords, LDAP bind credentials, database passwords, and any API keys or service account credentials stored on the server. If the server was compromised, attackers may have extracted these credentials for persistent access even after patching.
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Implement network segmentation and monitoring. Place the Zimbra server in a dedicated network segment with strict ingress and egress filtering. Monitor outbound connections from the mail server for unusual destinations or protocols that could indicate active command-and-control communication or data exfiltration from a prior compromise.
Technical Details
CVE-2024-45519 carries a CVSS v3.1 vector of CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H, yielding the maximum base score of 10.0 (Critical). Every metric represents the worst case: network-accessible (AV:N), low complexity (AC:L), no privileges required (PR:N), no user interaction needed (UI:N), and changed scope (S:C) meaning the vulnerability impacts resources beyond the vulnerable component.
The vulnerability resides in Zimbra's postjournal service, a component responsible for email journaling functionality that records copies of email communications for compliance and archival purposes. The postjournal service listens for incoming messages and processes them through a pipeline that includes shell command invocations. The critical flaw is that user-controlled content from incoming email messages is incorporated into these shell commands without proper sanitization or escaping. An attacker can craft SMTP messages with specially formatted headers or body content that include shell metacharacters and command sequences, which are then interpreted by the shell when the postjournal service processes the message.
The changed scope (S:C) is significant because the vulnerability in the postjournal service component allows code execution at the operating system level, impacting the entire server infrastructure beyond just the Zimbra mail service. The command execution occurs with the privileges of the Zimbra user account, which typically has broad access to the email store, configuration files, LDAP directory, and database. Affected versions span the entire Zimbra product line: versions prior to 8.8.15, the 8.8.15 release without Patch 46, 9.0.0 without Patch 41, 10.0.x before 10.0.9, and 10.1.0 before 10.1.1.
Frequently Asked Questions
What is CVE-2024-45519?
CVE-2024-45519 is a critical command injection vulnerability in the postjournal service of Zimbra Collaboration Suite that allows unauthenticated attackers to execute arbitrary operating system commands on the mail server. With the maximum CVSS score of 10.0, it represents a complete compromise of affected Zimbra installations.
Is CVE-2024-45519 being actively exploited?
Yes, extensively. The vulnerability has an EPSS score of 94.11% at the 99.9th percentile, placing it among the most exploited vulnerabilities globally. A public proof-of-concept exploit is available, and mass scanning campaigns targeting vulnerable Zimbra servers have been widely observed since its disclosure.
What is the postjournal service?
The postjournal service is a Zimbra component that handles email journaling, which records copies of email messages for compliance, legal, and archival purposes. It processes incoming messages through a pipeline that includes system command execution, and the vulnerability exploits insufficient input sanitization in this pipeline.
Should I assume my Zimbra server was compromised?
If your Zimbra server was running a vulnerable version and was accessible from the internet, you should treat it as potentially compromised. The vulnerability requires no authentication and was massively exploited before many organizations could patch. Conduct a thorough forensic investigation looking for web shells, unauthorized cron jobs, SSH keys, and unusual network activity before and after patching.
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