Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. In affected versions after Envoy sends a locally generated response it must stop further processing of request or response data. However when local response is generated due the internal buffer overflow while request or response is processed by the filter chain the operation may not be stopped completely and result in accessing a freed memory block. A specifically constructed request delivered by an untrusted downstream or upstream peer in the presence of extensions that modify and increase the size of request or response bodies resulting in a Denial of Service when using extensions that modify and increase the size of request or response bodies, such as decompressor filter. Envoy versions 1.19.1, 1.18.4, 1.17.4, 1.16.5 contain fixes to address incomplete termination of request processing after locally generated response. As a workaround disable Envoys decompressor, json-transcoder or grpc-web extensions or proprietary extensions that modify and increase the size of request or response bodies, if feasible.
Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Envoy | Envoyproxy | 1.16.0 (including) | 1.16.5 (excluding) |
| Envoy | Envoyproxy | 1.17.0 (including) | 1.17.4 (excluding) |
| Envoy | Envoyproxy | 1.18.0 (including) | 1.18.4 (excluding) |
| Envoy | Envoyproxy | 1.19.0 (including) | 1.19.0 (including) |
| OpenShift Service Mesh 1.1 | RedHat | servicemesh-proxy-0:1.1.17-2.el8 | * |
| OpenShift Service Mesh 2.0 | RedHat | servicemesh-proxy-0:2.0.7-3.el8 | * |
The use of previously-freed memory can have any number of adverse consequences, ranging from the corruption of valid data to the execution of arbitrary code, depending on the instantiation and timing of the flaw. The simplest way data corruption may occur involves the system’s reuse of the freed memory. Use-after-free errors have two common and sometimes overlapping causes:
In this scenario, the memory in question is allocated to another pointer validly at some point after it has been freed. The original pointer to the freed memory is used again and points to somewhere within the new allocation. As the data is changed, it corrupts the validly used memory; this induces undefined behavior in the process. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.