Oracle HTTP Server & WebLogic Server Proxy Plug-in Critical Vulnerability Advisory (CVE-2026-21962)

1. Apply Official Security Patches

Apply the appropriate patches provided in the Oracle Critical Patch Update (CPU) advisory immediately.

• Reference: Oracle Security Advisory (CPU Jan 2026)

2. Temporary Mitigations

If immediate patching is not feasible, implement the following workarounds:

A. Web Application Firewall (WAF) Rules

Configure WAF rules to inspect and block anomalous HTTP requests targeting the proxy plug-in. Specifically, sanitize or strip untrusted WebLogic-specific proxy headers at the ingress proxy/load balancer level:

# Example: Strip WebLogic proxy headers at the reverse proxy layer
proxy_set_header WL-Proxy-Client-IP "";
proxy_set_header WL-Proxy-SSL "";

B. Network Segmentation and Access Control Lists (ACLs)

Restrict direct internet access to the Oracle HTTP Server and WebLogic Proxy ports. Ensure that only trusted IP addresses or internal networks can communicate with these endpoints.

Technical Analysis & Exploit Mechanics

CVE-2026-21962 is a critical improper access control vulnerability (CWE-284) residing in the Oracle HTTP Server (OHS) and WebLogic Server Proxy Plug-in components of Oracle Fusion Middleware.

The vulnerability allows an unauthenticated, remote attacker with network access via HTTP to bypass security boundaries. The core mechanics and impacts include:

• Access Control Bypass (CWE-284): Attackers can craft malicious HTTP requests that exploit the proxy plug-in's request-parsing logic, gaining unauthorized access to protected backend resources.
• Scope Change (S:C): Although the vulnerability exists within the proxy plug-in, successful exploitation allows attackers to compromise additional critical products and backend application servers connected to the proxy.
• Data Integrity & Confidentiality Loss: Attackers can perform unauthorized creation, deletion, or modification of critical data, or gain complete access to all data accessible by the OHS and WebLogic Proxy Plug-in.

With a CVSS 3.1 Base Score of 10.0 (AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N), this vulnerability requires no privileges or user interaction. It has been added to the CISA KEV catalog due to active exploitation in the wild, and its EPSS score is extremely high at 0.94 (94%), indicating an imminent threat.