CVE-2022-27924
Synacor Zimbra Collaboration Suite (ZCS) Command Injection Vulnerability
Description
CVE-2022-27924 is a command injection vulnerability in Synacor Zimbra Collaboration Suite (ZCS) that allows an attacker to inject memcache commands into a targeted instance, causing the overwrite of arbitrary cached entries. By manipulating the memcache protocol, an attacker can poison cached authentication data to steal plaintext credentials or redirect email traffic. CISA has added CVE-2022-27924 to its Known Exploited Vulnerabilities catalog, confirming active exploitation, and the vulnerability is known to be used in ransomware campaigns. With an EPSS score of 90.4% (99.6th percentile), this vulnerability has near-certain exploitation probability.
KEV Information
CVSS Score
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:NOpen in CalculatorCWEs
Affected Products
| Vendor | Product | Version |
|---|---|---|
| synacor | zimbra collaboration suite | 8.8.15; 9.0.0 |
Multiple CVSS Assessments
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
References
- https://wiki.zimbra.com/wiki/Security_Center(Vendor Advisory)
- https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P24(Release Notes, Vendor Advisory)
- https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories(Vendor Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2022-27924(US Government Resource)
Weakness Type
CWE-77: Improper Neutralization of Special Elements used in a Command ('Command Injection')
CVE-2022-27924 exploits command injection in the Zimbra Collaboration Suite where user-supplied input is incorporated into memcache protocol commands without proper sanitization. The vulnerability allows an attacker to inject additional memcache commands that manipulate the caching layer, overwriting cached authentication entries and other sensitive data stored in the memcache instance.
Learn more: CWE-77 — Improper Neutralization of Special Elements used in a Command ('Command Injection')
Impact Analysis
CVE-2022-27924 presents a critical risk to Zimbra Collaboration Suite deployments because the memcache command injection can be exploited to steal user credentials in plaintext. By poisoning cached authentication entries, an attacker can redirect authentication flows to capture credentials as users log into the email system. The attack is remotely exploitable without authentication, requiring no user interaction, making it particularly dangerous for internet-facing Zimbra instances. Confidentiality is severely impacted as user credentials can be stolen; integrity is compromised through cache poisoning that can redirect email traffic; and availability may be affected through cache manipulation. The confirmed use in ransomware campaigns and the EPSS score of 90.4% (99.6th percentile) confirm that this vulnerability is being widely exploited against Zimbra deployments.
Exploit Maturity
CISA has confirmed active exploitation of CVE-2022-27924 in the wild by adding it to the Known Exploited Vulnerabilities catalog on August 4, 2022, with a remediation deadline of August 25, 2022. This vulnerability is known to be used in ransomware campaigns, making it a critical threat. The EPSS score of 90.4% (99.6th percentile) indicates near-certain exploitation activity. The vulnerability is part of a series of Zimbra flaws (alongside CVE-2022-27925 and CVE-2022-37042) that have been extensively targeted by multiple threat groups, making unpatched Zimbra instances high-priority targets for both credential theft and ransomware deployment.
Remediation
- Apply Zimbra security updates immediately: Install the patches referenced in the Zimbra release notes for version 9.0.0 P24.1, which addresses the memcache command injection vulnerability.
- Audit for credential compromise: Assume that user credentials may have been compromised if the Zimbra instance was exposed to the internet while unpatched. Force password resets for all users and review authentication logs for suspicious activity.
- Restrict network access to memcache: Ensure that the memcache service is not directly accessible from untrusted networks. The memcache port should only accept connections from the Zimbra application server itself.
- Implement network-level access controls for Zimbra: Place the Zimbra instance behind a web application firewall that can detect and block memcache injection patterns in HTTP requests.
- Monitor for anomalous email behavior: Deploy monitoring for unusual email forwarding rules, authentication failures, and credential-based attacks that may indicate ongoing exploitation of the cache poisoning vulnerability.
Technical Details
CVE-2022-27924 is a memcache command injection vulnerability in Synacor Zimbra Collaboration Suite. The Zimbra application uses memcache as a caching layer for frequently accessed data including authentication tokens and routing information. The vulnerability exists because user-supplied input is incorporated into memcache protocol commands without proper neutralization of special characters that function as command delimiters in the memcache protocol. An attacker can inject CRLF (carriage return / line feed) sequences to terminate the intended memcache command and inject additional commands, such as SET operations that overwrite cached entries. By poisoning the authentication cache, the attacker can redirect login flows to capture plaintext credentials when users authenticate against the Zimbra server. The attack is unauthenticated and can be performed remotely against any Zimbra instance where the vulnerable web interface is accessible, making it a high-impact attack against email infrastructure.
Frequently Asked Questions
Is CVE-2022-27924 being actively exploited?
Yes. CISA has confirmed active exploitation of CVE-2022-27924 and the vulnerability is known to be used in ransomware campaigns. The EPSS score of 90.4% (99.6th percentile) indicates near-certain exploitation. This vulnerability is part of a series of actively exploited Zimbra flaws targeting email infrastructure.
What products are affected by CVE-2022-27924?
CVE-2022-27924 affects Synacor Zimbra Collaboration Suite (ZCS). The vulnerability is in the memcache command handling. Zimbra versions prior to 9.0.0 P24.1 are affected. Organizations running Zimbra should consult the release notes for specific version details.
How do I fix CVE-2022-27924?
Update to Zimbra version 9.0.0 P24.1 or later, which addresses the memcache command injection. After patching, force password resets for all users and audit authentication logs for signs of credential compromise. Restrict network access to the memcache service.
How severe is CVE-2022-27924?
CVE-2022-27924 is an extremely severe vulnerability with an EPSS score of 90.4% (99.6th percentile) and confirmed use in ransomware campaigns. The unauthenticated memcache command injection enables credential theft through cache poisoning, potentially compromising all user accounts on the affected Zimbra server.
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