Envoy is a high-performance edge/middle/service proxy. Envoy will crash when certain timeouts happen within the same interval. The crash occurs when the following are true: 1. hedge_on_per_try_timeout is enabled, 2. per_try_idle_timeout is enabled (it can only be done in configuration), 3. per-try-timeout is enabled, either through headers or configuration and its value is equal, or within the backoff interval of the per_try_idle_timeout. This issue has been addressed in released 1.29.1, 1.28.1, 1.27.3, and 1.26.7. Users are advised to upgrade. There are no known workarounds for this vulnerability.
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 | 1.26.0 (including) | 1.26.7 (excluding) |
| Envoy | Envoyproxy | 1.27.0 (including) | 1.27.3 (excluding) |
| Envoy | Envoyproxy | 1.28.0 (including) | 1.28.1 (excluding) |
| Envoy | Envoyproxy | 1.29.0 (including) | 1.29.1 (excluding) |
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.