CVE-2025-71275 in Collaboration Suite
Summary
by MITRE • 03/24/2026
Zimbra Collaboration Suite (ZCS) PostJournal service version 8.8.15 contains a command injection vulnerability that allows unauthenticated attackers to execute arbitrary system commands by exploiting improper sanitization of the RCPT TO parameter via SMTP injection. Attackers can inject shell expansion syntax through the RCPT TO parameter to achieve remote code execution under the Zimbra service context.
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Analysis
by VulDB Data Team • 05/12/2026
The vulnerability in Zimbra Collaboration Suite PostJournal service version 8.8.15 represents a critical command injection flaw that exposes the system to remote code execution attacks. This issue stems from inadequate input validation and sanitization within the SMTP processing pipeline, specifically targeting the RCPT TO parameter handling mechanism. The vulnerability is classified as CWE-77 according to the Common Weakness Enumeration catalog, which details improper neutralization of special elements used in command execution contexts. The attack vector leverages the SMTP protocol's inherent trust model where the RCPT TO parameter is processed without sufficient sanitization, creating an opportunity for malicious actors to inject shell commands that will be executed with the privileges of the Zimbra service account.
The technical exploitation of this vulnerability occurs through carefully crafted SMTP transactions where attackers manipulate the RCPT TO parameter to include shell expansion syntax such as backticks, dollar signs, or other command substitution mechanisms. When the PostJournal service processes these malformed parameters, it fails to properly sanitize the input before passing it to system execution functions, resulting in arbitrary command execution. This flaw operates at the application layer and requires no authentication, making it particularly dangerous as attackers can exploit it remotely without prior access credentials. The execution context of the injected commands is confined to the Zimbra service account privileges, which typically have significant system access but may be restricted by the service's operational configuration.
The operational impact of this vulnerability extends beyond simple command execution to potentially compromise the entire Zimbra server infrastructure. Attackers who successfully exploit this vulnerability can execute arbitrary commands with the privileges of the Zimbra service account, which may include reading sensitive configuration files, accessing user mailboxes, modifying system files, or establishing persistent backdoors. The vulnerability's unauthenticated nature means that any external party can attempt exploitation, making it a high-priority target for malicious actors. According to ATT&CK framework's T1059.001 technique for Command and Scripting Interpreter, this vulnerability directly enables adversaries to execute commands through various shell interfaces, while T1078.004 covers legitimate account use for persistence, which could be achieved through this exploitation vector.
Mitigation strategies for this vulnerability should focus on immediate patching of the Zimbra Collaboration Suite to version 8.8.16 or later, which contains the necessary input sanitization fixes. Organizations should also implement network-level restrictions to limit SMTP access to trusted sources only, and deploy email filtering solutions that can detect and block suspicious RCPT TO parameter patterns. The implementation of proper input validation at the SMTP processing layer, including the use of allowlists for email address formats, can prevent the exploitation of this specific vulnerability. Additionally, monitoring for unusual command execution patterns and implementing intrusion detection systems can help identify potential exploitation attempts. Security teams should also consider implementing principle of least privilege for the Zimbra service account and regularly review system access controls to minimize the potential impact of successful exploitation.