Wasmtime is a standalone runtime for WebAssembly. Prior to version 2.0.2, there is a bug in Wasmtimes implementation of its pooling instance allocator where when a linear memory is reused for another instance the initial heap snapshot of the prior instance can be visible, erroneously to the next instance. This bug has been patched and users should upgrade to Wasmtime 2.0.2. Other mitigations include disabling the pooling allocator and disabling the memory-init-cow.
The product releases a resource such as memory or a file so that it can be made available for reuse, but it does not clear or “zeroize” the information contained in the resource before the product performs a critical state transition or makes the resource available for reuse by other entities.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Wasmtime | Bytecodealliance | * | 1.0.2 (excluding) |
| Wasmtime | Bytecodealliance | 2.0.0 (including) | 2.0.2 (excluding) |
| Firefox | Ubuntu | bionic | * |
| Firefox | Ubuntu | focal | * |
| Firefox | Ubuntu | trusty | * |
| Firefox | Ubuntu | xenial | * |
| Mozjs38 | Ubuntu | bionic | * |
| Mozjs38 | Ubuntu | esm-apps/bionic | * |
| Mozjs38 | Ubuntu | upstream | * |
| Mozjs52 | Ubuntu | bionic | * |
| Mozjs52 | Ubuntu | esm-apps/focal | * |
| Mozjs52 | Ubuntu | esm-infra/bionic | * |
| Mozjs52 | Ubuntu | focal | * |
| Mozjs52 | Ubuntu | upstream | * |
| Mozjs68 | Ubuntu | focal | * |
| Mozjs68 | Ubuntu | upstream | * |
| Mozjs78 | Ubuntu | esm-apps/jammy | * |
| Mozjs78 | Ubuntu | jammy | * |
| Mozjs78 | Ubuntu | kinetic | * |
| Mozjs78 | Ubuntu | lunar | * |
| Mozjs78 | Ubuntu | upstream | * |
| Mozjs91 | Ubuntu | jammy | * |
| Mozjs91 | Ubuntu | upstream | * |
| Thunderbird | Ubuntu | bionic | * |
| Thunderbird | Ubuntu | devel | * |
| Thunderbird | Ubuntu | focal | * |
| Thunderbird | Ubuntu | jammy | * |
| Thunderbird | Ubuntu | kinetic | * |
| Thunderbird | Ubuntu | lunar | * |
| Thunderbird | Ubuntu | mantic | * |
| Thunderbird | Ubuntu | noble | * |
| Thunderbird | Ubuntu | trusty | * |
| Thunderbird | Ubuntu | xenial | * |
When resources are released, they can be made available for reuse. For example, after memory is de-allocated, an operating system may make the memory available to another process, or disk space may be reallocated when a file is deleted. As removing information requires time and additional resources, operating systems do not usually clear the previously written information. Even when the resource is reused by the same process, this weakness can arise when new data is not as large as the old data, which leaves portions of the old data still available. Equivalent errors can occur in other situations where the length of data is variable but the associated data structure is not. If memory is not cleared after use, the information may be read by less trustworthy parties when the memory is reallocated. This weakness can apply in hardware, such as when a device or system switches between power, sleep, or debug states during normal operation, or when execution changes to different users or privilege levels.