CVE-2025-25235

Executive Summary

CVE-2025-25235 is a Server-Side Request Forgery (SSRF) vulnerability in Omnissa Secure Email Gateway (SEG). An unauthenticated attacker can exploit this flaw to route HTTP requests to internal networks, potentially accessing sensitive internal services, cloud metadata endpoints, or performing internal reconnaissance. The vulnerability affects SEG versions prior to 2.32 on Windows and prior to 2503 on UAG. With a CVSS score of 8.6, this is a high-severity issue that requires immediate attention. No public proof-of-concept (PoC) or exploit code has been released at this time.

CVSS Breakdown & Threat Level

• CVSS Score: 8.6 (High)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: High (C:H)
• Integrity Impact: None (I:N)
• Availability Impact: None (A:N)

The threat level is High due to the low attack complexity and the potential for significant internal network reconnaissance and data exfiltration.

Deep Dive & Mechanics

The vulnerability resides in the Omnissa Secure Email Gateway's handling of user-supplied URLs or redirects. The SEG application fails to properly validate or restrict the destination of HTTP requests made on behalf of the user. An attacker can craft a malicious request that forces the SEG server to make an HTTP request to an arbitrary internal IP address or hostname.

Attack Flow:

1. An attacker sends a specially crafted HTTP request to the SEG (e.g., a URL parameter or a redirect endpoint).
2. The SEG processes the request and initiates an outbound HTTP connection to the attacker-specified target.
3. Because the SEG does not filter internal IP ranges (e.g., 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, 127.0.0.0/8), the request can reach internal services.
4. The attacker can then read the response from the internal service, potentially leaking sensitive data (e.g., cloud metadata, internal API keys, configuration files).

This is a classic SSRF vulnerability (CWE-918) that can be used to pivot from the internet-facing SEG into the internal network.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

# Vulnerable SEG endpoint
def handle_redirect(request):
    target_url = request.GET.get('url')
    # No validation of target_url
    response = requests.get(target_url)
    return response.content

Patched Code (Conceptual):

# Patched SEG endpoint
import ipaddress

def handle_redirect(request):
    target_url = request.GET.get('url')
    parsed = urlparse(target_url)
    host = parsed.hostname
    try:
        ip = socket.gethostbyname(host)
        if ipaddress.ip_address(ip).is_private:
            return "Access denied", 403
    except:
        return "Invalid host", 400
    response = requests.get(target_url)
    return response.content

The patch adds IP address validation to block requests to private (internal) IP ranges.

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Deploy a vulnerable Omnissa SEG instance (version < 2.32 on Windows or < 2503 on UAG).
2. Set up an internal HTTP server (e.g., on 192.168.1.100:8080) serving a simple page with sensitive data.
3. From an external machine, send the following request:

curl -v "http://<SEG_IP>/redirect?url=http://192.168.1.100:8080/secret.txt"

Expected Result: The SEG fetches the internal resource and returns its content to the attacker.

Advanced Exploitation:

• Access cloud metadata endpoints (e.g., http://169.254.169.254/latest/meta-data/ on AWS).
• Scan internal ports using timing attacks or error messages.
• Use the SEG as a proxy to access other internal services.

Blue Team

Detection:

• Monitor outbound HTTP requests from the SEG server to internal IP ranges.
• Look for anomalous URL parameters containing internal IP addresses or hostnames.
• Alert on requests to cloud metadata IPs (169.254.169.254, 100.100.100.200, etc.).

Hunting:

• Search logs for url parameters containing private IPs (10.x.x.x, 172.16-31.x.x, 192.168.x.x).
• Check for unusual HTTP response sizes from the SEG (indicating internal data exfiltration).

Indicators of Compromise (IOCs)

• Network IOCs:

  • Outbound HTTP requests from SEG to internal IP ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, 127.0.0.0/8).
  • Requests to cloud metadata IPs (169.254.169.254, 100.100.100.200, 169.254.169.253).
  • Unusual Host headers in SEG logs pointing to internal hostnames.

• File IOCs:

  • Log entries containing url parameter with internal IPs.
  • Temporary files created by the SEG containing internal data.

• Behavioral IOCs:

  • SEG making HTTP requests to non-email-related services.
  • Increased outbound traffic from the SEG server.

Detection Engineering

YARA Rule

rule CVE_2025_25235_SSRF_Omnissa_SEG {
    meta:
        description = "Detects SSRF attempts against Omnissa SEG via URL parameters"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-25235"
    strings:
        $url_param = "url=" nocase
        $internal_ip = /(10\.\d{1,3}\.\d{1,3}\.\d{1,3}|172\.(1[6-9]|2\d|3[01])\.\d{1,3}\.\d{1,3}|192\.168\.\d{1,3}\.\d{1,3}|127\.\d{1,3}\.\d{1,3}\.\d{1,3})/
        $metadata_ip = /169\.254\.169\.\d{1,3}/
    condition:
        $url_param and ($internal_ip or $metadata_ip)
}

Sigma Rule

title: CVE-2025-25235 SSRF Attempt Against Omnissa SEG
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects HTTP requests to internal IPs from Omnissa SEG
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: omnissa_seg
detection:
    selection:
        cs-uri-query|contains: "url="
        c-ip|startswith:
            - "10."
            - "172.16."
            - "172.17."
            - "172.18."
            - "172.19."
            - "172.20."
            - "172.21."
            - "172.22."
            - "172.23."
            - "172.24."
            - "172.25."
            - "172.26."
            - "172.27."
            - "172.28."
            - "172.29."
            - "172.30."
            - "172.31."
            - "192.168."
            - "127."
            - "169.254."
    condition: selection
falsepositives:
    - Legitimate internal redirects (if any)
level: high

Suricata Rule

alert http $EXTERNAL_NET any -> $HOME_NET any (
    msg:"CVE-2025-25235 SSRF Attempt Against Omnissa SEG";
    flow:to_server;
    content:"url="; http_uri;
    pcre:"/url=(https?:\/\/)?(10\.\d{1,3}\.\d{1,3}\.\d{1,3}|172\.(1[6-9]|2\d|3[01])\.\d{1,3}\.\d{1,3}|192\.168\.\d{1,3}\.\d{1,3}|127\.\d{1,3}\.\d{1,3}\.\d{1,3}|169\.254\.\d{1,3}\.\d{1,3})/i";
    sid:10000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Patch: Upgrade Omnissa SEG to version 2.32 (Windows) or 2503 (UAG) immediately.
2. Workaround: If patching is not possible, implement a Web Application Firewall (WAF) rule to block requests containing url= parameters pointing to private IP ranges.
3. Network Segmentation: Ensure the SEG server has minimal outbound access to internal networks. Use firewall rules to block outbound traffic from the SEG to private IP ranges.

Long-Term Fixes:

• Implement strict input validation for all URL parameters.
• Use an allowlist of permitted external domains for redirects.
• Regularly audit and update all network-facing applications.

Valters IT Signature

This report was generated by Valters IT DevSecOps AI Assistant.