Threats tagged 'ghsa-crwc-vw2r-qr6m'

### 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 consults on every constructor and method call. Frameworks that evaluate untrusted expressions are expected to install a restrictive `MemberAccess` — for example, Apache Struts' `SecurityMemberAccess`, which excludes dangerous classes and the `java.lang.reflect` package. Against such a `MemberAccess` this PoC is blocked at the very first step (the `new ProcessBuilder(...)` constructor), before reflection is ever reachable. The default context that ships with OGNL intentionally allows all public members and is **not** designed to sandbox untrusted input. An application that evaluates attacker-controlled expressions with that permissive default already has many paths to code execution, and this technique is not required to achieve it. **You are affected only if all of the following hold:** (1) your application evaluates untrusted/attacker-controlled OGNL expressions, (2) it uses OGNL's default permissive `MemberAccess` (or an equivalently permissive one that allows `java.lang.reflect`), and (3) it relies on the stricter-invocation block list as its sandbox. **Properly configured consumers — including Apache Struts with its `SecurityMemberAccess` — are not affected.** The actual protection for untrusted-expression scenarios remains a correctly configured `MemberAccess`; the block list should not be treated as a sandbox. ### Fix `java.lang.reflect.Method`, `java.lang.reflect.Constructor`, and `java.lang.reflect.Field` are added to the stricter-invocation block list, so reflection objects can no longer be used as invocation proxies in stricter mode. The `java.lang.invoke.MethodHandle` path was verified not to be exploitable (its signature-polymorphic `invoke`/`invokeExact` fail through OGNL's reflection-based invocation), so no additional classes are required. ### Credit Reported responsibly through Tidelift by 毛锐 (youyi.mr@alibaba-inc.com).