A severe Cross-Site Request Forgery (CSRF) vulnerability in Zimbra Collaboration Suite (ZCS) versions 9.0 to 10.1 has put email servers and user data at risk of exploitation.
Tracked as CVE-2025-32354, the flaw allows attackers to hijack authenticated sessions and steal sensitive information, including passwords, contacts, and email content.
The flaw resides in Zimbra’s GraphQL endpoint (/service/extension/graphql), which lacks CSRF token validation.
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Attackers can craft malicious websites or links that trigger unauthorized GraphQL operations when visited by a logged-in Zimbra user. This enables threat actors to:
- Modify or export a victim’s contact list.
- Change account settings (e.g., passwords, auto-forwarding rules).
- Access emails, calendars, and file-sharing permissions.
- Potentially escalate privileges to compromise entire domains.
Unlike traditional CSRF attacks, this exploit leverages GraphQL’s flexible query structure to bypass standard security checks.
Impact and Exploit Risks
Zimbra Collaboration, used by over 200,000 organizations globally, is a prime target for phishing and data exfiltration campaigns. Successful exploitation could lead to:
- Corporate espionage: Theft of confidential communications.
- Account takeovers: Attackers reroute emails or lock users out.
- Credential harvesting: Stolen passwords reused for lateral attacks.
Mitigation and Patches
Zimbra released version 10.1.1 on April 28, 2025, to address the flaw. Admins are urged to:
- Upgrade immediately to the patched version.
- Enforce CSRF tokens via headers like X-Zimbra-CSRF-Token for GraphQL requests.
- Audit logs for unusual GraphQL activity (e.g., unexpected contact exports).
For organizations unable to upgrade, temporary fixes include:
- Restricting access to the GraphQL endpoint.
- Implementing reverse proxy rules to validate request origins.
In an advisory, Zimbra confirmed the vulnerability’s severity and emphasized that cloud-hosted instances were patched automatically.
On-premises users must manually apply updates. The company also recommended enabling multi-factor authentication (MFA) to reduce session hijacking risks.
- Verify your ZCS version under Admin Console > Maintenance.
- Train employees to avoid suspicious links, even from known contacts.
- Monitor Zimbra’s security portal for future advisories.
CSRF flaws remain a persistent threat in web applications. This incident underscores the need for robust token-based authentication mechanisms, especially in collaboration tools handling sensitive data.
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