CVE-2025-25235: Omnissa Secure Email Gateway SSRF Flaw

CVE-2025-25235 Overview

CVE-2025-25235 is a Server-Side Request Forgery (SSRF) vulnerability affecting Omnissa Secure Email Gateway (SEG). This vulnerability exists in SEG versions prior to 2.32 running on Windows and SEG versions prior to 2503 running on UAG (Unified Access Gateway). The flaw allows attackers to route network traffic, including HTTP requests, to internal networks that should not be accessible from external sources.

SSRF vulnerabilities in email gateway products are particularly dangerous as these systems typically sit at network boundaries with access to both external and internal resources. Successful exploitation could enable attackers to access internal services, enumerate internal infrastructure, or pivot to other attacks against backend systems.

Critical Impact

Unauthenticated attackers can exploit this SSRF vulnerability to access internal network resources from the internet, potentially exposing sensitive internal services and data with high confidentiality impact.

Affected Products

• Omnissa Secure Email Gateway (SEG) prior to version 2.32 on Windows
• Omnissa Secure Email Gateway (SEG) prior to version 2503 on UAG (Unified Access Gateway)

Discovery Timeline

• 2025-08-11 - CVE-2025-25235 published to NVD
• 2025-08-12 - Last updated in NVD database

Technical Details for CVE-2025-25235

Vulnerability Analysis

This vulnerability is classified under CWE-918 (Server-Side Request Forgery), which occurs when a web application fetches remote resources based on user-supplied input without properly validating the destination. In the context of Omnissa Secure Email Gateway, the application can be manipulated to make HTTP requests to arbitrary internal network destinations.

Email gateway systems process incoming email traffic and often need to interact with various backend services for authentication, policy enforcement, and content filtering. When input validation is insufficient, attackers can abuse these server-side request capabilities to access internal resources that would otherwise be protected by network segmentation.

The vulnerability requires no authentication and no user interaction, making it exploitable by any network-adjacent attacker who can reach the vulnerable SEG instance. The scope is changed, meaning successful exploitation can impact resources beyond the vulnerable component itself—specifically, internal network services that the SEG can reach.

Root Cause

The root cause is improper input validation in the Omnissa Secure Email Gateway that fails to adequately restrict or sanitize user-controlled input used in server-side HTTP requests. This allows attackers to specify arbitrary URLs or network destinations, bypassing intended access restrictions. The application does not implement proper allowlisting of permitted destinations or fails to block requests to internal IP ranges and sensitive network locations.

Attack Vector

The attack vector is network-based, requiring no privileges and no user interaction. An attacker can craft malicious requests to the vulnerable SEG instance that include attacker-controlled URLs or IP addresses. The server then processes these requests and initiates connections to the specified destinations from its trusted network position.

Typical SSRF attack scenarios against this vulnerability may include:

• Accessing internal web services and APIs not exposed to the internet
• Scanning internal network infrastructure to identify live hosts and services
• Retrieving cloud instance metadata from services like AWS (169.254.169.254)
• Bypassing firewall rules that trust traffic originating from the SEG server
• Exfiltrating sensitive data from internal systems that trust requests from the gateway

The vulnerability has high confidentiality impact but no direct integrity or availability impact, indicating attackers can read sensitive information but cannot directly modify data or cause service disruption through this vector alone.

Detection Methods for CVE-2025-25235

Indicators of Compromise

• Unusual outbound HTTP requests from the SEG server to internal IP addresses or RFC 1918 ranges
• Requests to cloud metadata endpoints (e.g., 169.254.169.254) originating from the SEG server
• Anomalous network traffic patterns from the email gateway to internal services it typically does not communicate with
• Log entries showing requests with URLs containing internal hostnames or IP addresses in unexpected parameters

Detection Strategies

• Monitor SEG server network traffic for connections to internal IP ranges that are not part of normal email processing workflows
• Implement network-level detection rules for SSRF patterns including requests to localhost, internal ranges, and cloud metadata services
• Review application logs for unusual URL patterns or error messages indicating failed internal connections
• Deploy web application firewall (WAF) rules to detect SSRF payloads in incoming requests to the SEG

Monitoring Recommendations

• Enable detailed logging on the Omnissa SEG to capture all outbound HTTP requests with full URL information
• Configure SIEM alerts for network connections from the SEG server to internal subnets outside its normal communication patterns
• Implement egress filtering monitoring to detect attempts to reach sensitive internal services from the DMZ
• Regularly audit SEG configuration and access logs for signs of reconnaissance or exploitation attempts

How to Mitigate CVE-2025-25235

Immediate Actions Required

• Upgrade Omnissa Secure Email Gateway on Windows to version 2.32 or later immediately
• Upgrade Omnissa Secure Email Gateway on UAG to version 2503 or later immediately
• Review network segmentation to limit the SEG's ability to reach sensitive internal resources
• Implement egress filtering to restrict outbound connections from the SEG server to only necessary destinations

Patch Information

Omnissa has released security patches to address this vulnerability. Organizations should apply the appropriate update based on their deployment:

• Windows deployments: Update to SEG version 2.32 or later
• UAG deployments: Update to SEG version 2503 or later

For complete patch details and download information, refer to the Omnissa Security Advisory OMSA-2025-0003.

Workarounds

• Implement strict network segmentation to isolate the SEG from sensitive internal resources until patching is complete
• Configure network-level access controls to limit which internal destinations the SEG server can reach
• Deploy a web application firewall (WAF) with SSRF detection capabilities in front of the SEG
• Block outbound requests from the SEG to cloud metadata IP addresses and internal RFC 1918 ranges at the network level
• Enable request logging and monitoring to detect exploitation attempts while awaiting patching

# Example network-level mitigation: Block common SSRF targets from SEG server
# Add firewall rules to block internal network access from SEG
# Note: Adjust IP ranges based on your network architecture

# Block access to cloud metadata services
iptables -A OUTPUT -s <SEG_SERVER_IP> -d 169.254.169.254 -j DROP

# Block access to internal RFC 1918 ranges (adjust as needed)
iptables -A OUTPUT -s <SEG_SERVER_IP> -d 10.0.0.0/8 -j DROP
iptables -A OUTPUT -s <SEG_SERVER_IP> -d 172.16.0.0/12 -j DROP
iptables -A OUTPUT -s <SEG_SERVER_IP> -d 192.168.0.0/16 -j DROP

# Allow only necessary outbound connections (whitelist approach)
# Example: Allow SMTP relay to specific mail servers
iptables -A OUTPUT -s <SEG_SERVER_IP> -d <MAIL_SERVER_IP> -p tcp --dport 25 -j ACCEPT