CVE-2025-25065: Zimbra Collaboration Suite SSRF Vulnerability

CVE-2025-25065 Overview

CVE-2025-25065 is a Server-Side Request Forgery (SSRF) vulnerability discovered in the RSS feed parser component of Zimbra Collaboration Suite. This vulnerability allows unauthenticated remote attackers to redirect requests to internal network endpoints, potentially exposing sensitive internal services and infrastructure that should not be accessible from external networks.

The flaw exists in how Zimbra's RSS feed parser processes user-supplied URLs. By crafting malicious RSS feed URLs, attackers can manipulate the server into making requests to arbitrary internal resources, bypassing network segmentation and firewall protections.

Critical Impact

Attackers can leverage this SSRF vulnerability to access internal network services, potentially leading to information disclosure, internal service enumeration, and further exploitation of backend systems that are not directly accessible from the internet.

Affected Products

• Zimbra Collaboration Suite 9.0.0 before Patch 43
• Zimbra Collaboration Suite 10.0.x before 10.0.12
• Zimbra Collaboration Suite 10.1.x before 10.1.4

Discovery Timeline

• February 3, 2025 - CVE-2025-25065 published to NVD
• June 11, 2025 - Last updated in NVD database

Technical Details for CVE-2025-25065

Vulnerability Analysis

This Server-Side Request Forgery vulnerability resides in Zimbra Collaboration Suite's RSS feed parser functionality. The parser fails to properly validate and restrict the destination of outbound HTTP requests when processing RSS feed URLs provided by users.

When a user configures or subscribes to an RSS feed within Zimbra, the server-side component fetches the feed content from the specified URL. The vulnerability arises because the parser does not adequately filter or block requests targeting internal network addresses, localhost, or private IP ranges.

An attacker can exploit this by supplying a malicious RSS feed URL pointing to internal services such as metadata endpoints, administration interfaces, or other backend services. Since the request originates from the Zimbra server itself, it bypasses external network controls and can access resources that would otherwise be unreachable from the attacker's position.

This vulnerability is classified under CWE-918 (Server-Side Request Forgery), which describes the weakness where a web application does not properly validate user-supplied URLs before making requests to them.

Root Cause

The root cause of CVE-2025-25065 is insufficient input validation in the RSS feed parser module. Specifically, the Zimbra application fails to implement proper URL validation and filtering mechanisms that would prevent requests to:

• Private IP address ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16)
• Localhost addresses (127.0.0.0/8)
• Link-local addresses (169.254.0.0/16)
• Cloud provider metadata endpoints (e.g., 169.254.169.254)

The absence of an allowlist or blocklist approach for outbound requests from the RSS parser creates the attack surface for SSRF exploitation.

Attack Vector

The attack vector for this vulnerability is network-based and requires no authentication or user interaction. An attacker can exploit the vulnerability through the following mechanism:

1. The attacker identifies a Zimbra Collaboration Suite instance exposed to the internet
2. The attacker crafts a malicious RSS feed URL targeting internal network resources
3. The attacker submits this URL through the RSS feed subscription functionality
4. The Zimbra server processes the request and makes an outbound connection to the attacker-specified internal endpoint
5. The response from the internal service may be returned to the attacker or trigger unintended actions on internal systems

Common exploitation targets include internal web applications, cloud metadata services, and administrative interfaces. The vulnerability can be used for internal port scanning, service enumeration, and potentially accessing sensitive configuration data or credentials stored in internal services.

Detection Methods for CVE-2025-25065

Indicators of Compromise

• Unusual outbound HTTP/HTTPS requests from Zimbra servers to internal IP ranges
• RSS feed subscriptions containing private IP addresses, localhost, or cloud metadata endpoints
• Unexpected network connections from Zimbra to internal services on non-standard ports
• Log entries showing RSS feed parsing errors for internal network addresses

Detection Strategies

• Monitor Zimbra server network traffic for connections to RFC 1918 private address ranges
• Implement network-level detection rules for outbound connections from mail servers to sensitive internal endpoints
• Review Zimbra logs for RSS feed subscription activities with suspicious URL patterns
• Deploy intrusion detection signatures to identify SSRF attack patterns targeting RSS functionality

Monitoring Recommendations

• Enable detailed logging for RSS feed parser activities in Zimbra
• Configure network monitoring to alert on Zimbra server connections to internal infrastructure
• Implement egress filtering at the network perimeter to restrict outbound connections from mail servers
• Regularly audit RSS feed subscriptions for potentially malicious URL entries

How to Mitigate CVE-2025-25065

Immediate Actions Required

• Upgrade Zimbra Collaboration Suite 9.0.0 to Patch 43 or later
• Upgrade Zimbra Collaboration Suite 10.0.x to version 10.0.12 or later
• Upgrade Zimbra Collaboration Suite 10.1.x to version 10.1.4 or later
• Review and audit existing RSS feed subscriptions for malicious entries

Patch Information

Zimbra has released security patches addressing this vulnerability across all affected version branches. Organizations should apply the appropriate patch based on their current Zimbra version:

• Version 9.0.0: Apply Patch 43
• Version 10.0.x: Upgrade to version 10.0.12 or later
• Version 10.1.x: Upgrade to version 10.1.4 or later

For complete security advisory information, refer to the Zimbra Security Advisories page.

Workarounds

• Implement network-level egress filtering to block Zimbra server connections to internal IP ranges
• Configure firewall rules to restrict outbound HTTP/HTTPS from Zimbra to known-good external destinations only
• Disable RSS feed functionality if not required for business operations
• Deploy a web application firewall (WAF) to inspect and filter RSS feed URL submissions

# Example iptables rules to restrict Zimbra server outbound connections to private IP ranges
# Apply these rules on the Zimbra server to mitigate SSRF attacks

# Block connections to private IP ranges (10.0.0.0/8)
iptables -A OUTPUT -m owner --uid-owner zimbra -d 10.0.0.0/8 -j DROP

# Block connections to private IP ranges (172.16.0.0/12)
iptables -A OUTPUT -m owner --uid-owner zimbra -d 172.16.0.0/12 -j DROP

# Block connections to private IP ranges (192.168.0.0/16)
iptables -A OUTPUT -m owner --uid-owner zimbra -d 192.168.0.0/16 -j DROP

# Block connections to localhost
iptables -A OUTPUT -m owner --uid-owner zimbra -d 127.0.0.0/8 -j DROP

# Block connections to cloud metadata endpoint
iptables -A OUTPUT -m owner --uid-owner zimbra -d 169.254.169.254 -j DROP