CVE-2026-1561 Overview
IBM WebSphere Application Server Liberty versions 17.0.0.3 through 26.0.0.3 are vulnerable to server-side request forgery (SSRF). This vulnerability may allow a remote attacker to send unauthorized requests from the system, potentially leading to network enumeration or facilitating other attacks against internal services.
Critical Impact
Remote attackers with low-level access can exploit this SSRF vulnerability to perform unauthorized requests from the vulnerable server, enabling internal network reconnaissance and potential lateral movement within the infrastructure.
Affected Products
- IBM WebSphere Application Server Liberty 17.0.0.3
- IBM WebSphere Application Server Liberty through 26.0.0.3
- All intermediate versions of IBM WebSphere Application Server Liberty
Discovery Timeline
- 2026-03-25 - CVE CVE-2026-1561 published to NVD
- 2026-03-26 - Last updated in NVD database
Technical Details for CVE-2026-1561
Vulnerability Analysis
This Server-Side Request Forgery (SSRF) vulnerability exists within IBM WebSphere Application Server Liberty, classified under CWE-918 (Server-Side Request Forgery). The vulnerability allows authenticated attackers to abuse the server's ability to make HTTP requests, causing the application to send crafted requests to arbitrary destinations.
The attack requires network access and low-level privileges, making it exploitable by authenticated users. The vulnerability impacts both confidentiality and integrity of the system without affecting availability. An attacker can leverage this flaw to access internal resources that are normally protected by network segmentation, enumerate internal network topology, and potentially pivot to attack other internal services.
Root Cause
The root cause of this vulnerability lies in insufficient validation and sanitization of user-supplied URLs or request parameters that are subsequently used by the server to make outbound HTTP requests. When the application processes these requests without proper validation, attackers can manipulate the destination to target internal resources, cloud metadata endpoints, or external systems.
Attack Vector
The attack is conducted remotely over the network. An authenticated attacker can craft malicious requests containing URLs pointing to internal network resources or sensitive endpoints. The server processes these requests and forwards them to the specified destinations, returning the responses to the attacker.
Common SSRF attack targets include:
- Internal microservices and APIs not exposed to the public internet
- Cloud metadata services (e.g., 169.254.169.254)
- Internal databases and caching systems
- Administrative interfaces on localhost or internal networks
The vulnerability requires authentication (low privileges) but does not require user interaction, making it suitable for automated exploitation in targeted attacks.
Detection Methods for CVE-2026-1561
Indicators of Compromise
- Unusual outbound HTTP requests from the WebSphere Application Server to internal IP ranges (10.x.x.x, 172.16.x.x, 192.168.x.x)
- Requests to cloud metadata endpoints such as 169.254.169.254
- HTTP requests to localhost (127.0.0.1) or loopback addresses originating from the application layer
- Unexpected connections to internal services on non-standard ports
Detection Strategies
- Monitor application server logs for requests containing internal IP addresses or localhost references in URL parameters
- Implement network segmentation monitoring to detect unauthorized cross-segment traffic from application servers
- Deploy web application firewall (WAF) rules to detect and block SSRF payload patterns in request parameters
- Enable SentinelOne's behavioral AI to detect anomalous network connections from application servers
Monitoring Recommendations
- Configure alerting for outbound connections from the WebSphere Application Server to RFC 1918 private address spaces
- Monitor DNS queries from the application server for resolution of internal hostnames
- Implement egress filtering and log all blocked outbound connection attempts
- Review HTTP access logs for encoded or obfuscated URL schemes that may indicate SSRF attempts
How to Mitigate CVE-2026-1561
Immediate Actions Required
- Apply the security patch provided by IBM as soon as possible
- Review and restrict the application server's ability to make outbound HTTP requests
- Implement network segmentation to limit the blast radius of potential SSRF exploitation
- Configure allow-lists for permitted outbound request destinations
- Audit application code for user-controllable URL inputs
Patch Information
IBM has released a security update addressing this vulnerability. Organizations running affected versions of IBM WebSphere Application Server Liberty (17.0.0.3 through 26.0.0.3) should apply the patch immediately. Detailed patch information and download links are available through the IBM Support Page.
Workarounds
- Implement strict input validation for any user-supplied URLs or parameters used in server-side requests
- Deploy network-level controls to block outbound requests to internal IP ranges from the application server
- Use a proxy server for all outbound requests with strict allow-listing of permitted destinations
- Disable or restrict access to vulnerable features until patches can be applied
- Configure web application firewall rules to block common SSRF payload patterns
# Example iptables rules to restrict outbound connections from application server
# Block connections to internal networks from the WebSphere process
iptables -A OUTPUT -m owner --uid-owner was -d 10.0.0.0/8 -j DROP
iptables -A OUTPUT -m owner --uid-owner was -d 172.16.0.0/12 -j DROP
iptables -A OUTPUT -m owner --uid-owner was -d 192.168.0.0/16 -j DROP
iptables -A OUTPUT -m owner --uid-owner was -d 169.254.169.254 -j DROP
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