OGNL is an Object Graph Navigation Library for Java. Prior to 3.4.13, the optional stricter-invocation mode in OgnlRuntime.invokeMethod checks the declaring class of the method that OGNL invokes but does not block java.lang.reflect.Method, java.lang.reflect.Constructor, or java.lang.reflect.Field. An attacker-controlled expression can invoke one of these reflection objects as a proxy for a method on a blocked class, causing the real operation to execute inside JDK reflection without passing through the stricter-invocation check again. Exploitation requires an application to evaluate untrusted OGNL expressions, use the default or an equivalently permissive MemberAccess that permits reflection, and rely on stricter invocation as a sandbox. Applications using a restrictive MemberAccess, including Apache Struts with SecurityMemberAccess, are not affected by this bypass. This issue is fixed in 3.4.13.

Affected: Maven: ognl:ognl

### Summary

OGNL's optional *stricter invocation* mode maintains a block list that prevents expressions from directly calling methods on dangerous classes such as `Runtime`, `ProcessBuilder`, and `ClassLoader`. The block list filters on the **declaring class of the method OGNL invokes**. Because `java.lang.reflect.Method` (and `Constructor`/`Field`) are not on the list, an expression can use reflection as a proxy — `someMethod.invoke(target, args)` — to reach a blocked method. The real call (e.g. `ProcessBuilder.start()`) then executes inside the JDK reflection machinery and never passes back through OGNL's `invokeMethod`, so the block list never sees it.

### Proof of concept

Under the default OGNL context (public-only access, stricter invocation enabled), the following expression creates a file even though a direct `new ProcessBuilder(...).start()` is blocked:

``` (#pb=new java.lang.ProcessBuilder({"/usr/bin/touch","rce-proof.txt"}), #methods=@java.lang.ProcessBuilder@class.getMethods(), #names=#methods.{ #this.getName() }, #startIdx=#names.indexOf("start"), #methods[#startIdx].invoke(#pb, null)) ```

### Impact and scope — please read carefully

**This is hardening of a defense-in-depth secondary layer, not a break of OGNL's primary security boundary.**

In OGNL the stricter-invocation block list is a *secondary* mitigation. The **primary** access-control gate is the `MemberAccess` implementation supplied by the integrating framework or application, which OGNL cons…

Affected: Ubuntu:16.04:LTS: ognl, Ubuntu:18.04:LTS: ognl, Ubuntu:20.04:LTS: ognl, Ubuntu:22.04:LTS: ognl, Ubuntu:24.04:LTS: ognl, Ubuntu:26.10: ognl, Ubuntu:26.04:LTS: ognl

(OGNL is an Object Graph Navigation Library for Java. Prior to 3.4.13, ...)