Zimbra’s RSS parser module fails to sufficiently validate or restrict external feed URLs. Because of this, an attacker can supply a malicious feed URL that forces Zimbra to make HTTP requests to internal or private network addresses. This server-side request forgery (SSRF) converts Zimbra itself into a proxy for internal reconnaissance.
Once the crafted URL is parsed, Zimbra issues the request to the target internal endpoint, such as admin consoles, metadata services, or internal API endpoints. The attacker then captures the response, leaking internal infrastructure details. Because this flaw lies within a legitimate feature RSS feeds defenders may overlook it as benign traffic.
Affected Versions & Vendor Response
The vulnerability is tracked as CVE-2025-25065, described by the NVD. Zimbra Collaboration versions earlier than 9.0.0 Patch 43, 10.0.x < 10.0.12, and 10.1.x < 10.1.4 are vulnerable. Zimbra has patched it in the listed versions and published advisory notes on feeds and handling restrictions.
Organizations still running vulnerable Zimbra versions must prioritize patching immediately. Delay elevates exposure to internal reconnaissance and lateral movement risks.
Attack Example & Internal Reconnaissance
An attacker might craft a malicious RSS feed link pointing to http://10.0.0.5/admin/health or http://127.0.0.1:9200/_cluster/health. When Zimbra fetches this feed, it unwittingly requests internal data, returning JSON or HTML content back to the attacker. The attacker can iterate over internal endpoints, extract service information, and map internal network structure.
Because Zimbra likely runs on a server with broader access than end-user machines, the SSRF becomes a powerful reconnaissance tool. From there, further exploitation or pivoting becomes possible, especially when combined with other vulnerabilities.
Mitigation and Defensive Strategies
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Immediately upgrade to Zimbra versions 10.0.12, 10.1.4, or higher.
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Limit Zimbra’s external URL fetch capability via network controls: block or whitelist allowed domains.
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Implement internal network segmentation to isolate sensitive endpoints from services like RSS.
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Monitor logs for outbound requests from Zimbra to internal addresses. Such anomalies can signal SSRF exploitation.
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Apply web application firewall (WAF) rules that detect SSRF patterns, such as internal IP ranges in outbound requests.
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Harden feed parser modules by sanitizing, validating, and sanitizing URL schemes and ports.
Wider Threat Landscape & Context
Zimbra is under increasing threat from multiple vulnerability classes. For example, besides SSRF, Zimbra has faced exploitation of SQL injection (CVE-2025-25064) in its SOAP endpoint and stored XSS (CVE-2025-27915) in its Classic Web Client. Attackers often chain SSRF findings with other flaws to gain deeper access or exfiltrate sensitive data.
Historically, Zimbra also had a remote code execution flaw (CVE-2024-45519) in its postjournal service. That vulnerability allowed attackers to encode shell commands in SMTP messages to gain system-level control. While that flaw is not directly related to this SSRF, its presence in the same ecosystem underscores the importance of layered defenses.
FAQs
Q1: Does this SSRF vulnerability allow remote code execution?
No. CVE-2025-25065 is strictly an SSRF that leaks internal data. By itself, it doesn’t provide arbitrary code execution unless chained with another bug.
Q2: How can I detect if Zimbra was exploited via SSRF?
Watch for unusual outbound HTTP requests from Zimbra processes to private IP ranges. Also check logs for RSS feed fetches targeting internal addresses.
Q3: Is limiting Zimbra’s outbound connectivity enough to block exploitation?
It helps significantly. Enforcing allowlists or blocking unauthorized URL fetches reduces attack surfaces drastically, though patching remains essential.
Q4: Can an attacker use this SSRF to reach the database server?
Possibly. If Zimbra has access to internal database or metadata endpoints, the SSRF request could fetch responses from those internal systems.
Q5: What version is safe from this SSRF?
Any Zimbra version 9.0.0 Patch 43, 10.0.12, or 10.1.4 and above includes the fix for CVE-2025-25065.
