CVE-2024-47813
LOWWasmtime race condition could lead to WebAssembly control-flow integrity and type safety violations
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
wasmtime🦀wasmtime🦀wasmtime🦀wasmtime🦀wasmtimeReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
Wasmtime is an open source runtime for WebAssembly. Under certain concurrent event orderings, a wasmtime::Engine's internal type registry was susceptible to double-unregistration bugs due to a race condition, leading to panics and potentially type registry corruption. That registry corruption could, following an additional and particular sequence of concurrent events, lead to violations of WebAssembly's control-flow integrity (CFI) and type safety. Users that do not use wasmtime::Engine across multiple threads are not affected. Users that only create new modules across threads over time are additionally not affected. Reproducing this bug requires creating and dropping multiple type instances (such as wasmtime::FuncType or wasmtime::ArrayType) concurrently on multiple threads, where all types are associated with the same wasmtime::Engine. Wasm guests cannot trigger this bug. See the "References" section below for a list of Wasmtime types-related APIs that are affected. Wasmtime maintains an internal registry of types within a wasmtime::Engine and an engine is shareable across threads. Types can be created and referenced through creation of a wasmtime::Module, creation of wasmtime::FuncType, or a number of other APIs where the host creates a function (see "References" below). Each of these cases interacts with an engine to deduplicate type information and manage type indices that are used to implement type checks in WebAssembly's call_indirect function, for example. This bug is a race condition in this management where the internal type registry could be corrupted to trigger an assert or contain invalid state. Wasmtime's internal representation of a type has individual types (e.g. one-per-host-function) maintain a registration count of how many time it's been used. Types additionally have state within an engine behind a read-write lock such as lookup/deduplication information. The race here is a time-of-check versus time-of-use (TOCTOU) bug where one thread atomically decrements a type entry's registration count, observes zero registrations, and then acquires a lock in order to unregister that entry. However, between when this first thread observed the zero-registration count and when it acquires that lock, another thread could perform the following sequence of events: re-register another copy of the type, which deduplicates to that same entry, resurrecting it and incrementing its registration count; then drop the type and decrement its registration count; observe that the registration count is now zero; acquire the type registry lock; and finally unregister the type. Now, when the original thread finally acquires the lock and unregisters the entry, it is the second time this entry has been unregistered. This bug was originally introduced in Wasmtime 19's development of the WebAssembly GC proposal. This bug affects users who are not using the GC proposal, however, and affects Wasmtime in its default configuration even when the GC proposal is disabled. Wasmtime users using 19.0.0 and after are all affected by this issue. We have released the following Wasmtime versions, all of which have a fix for this bug: * 21.0.2 * 22.0.1 * 23.0.3 * 24.0.1 * 25.0.2. If your application creates and drops Wasmtime types on multiple threads concurrently, there are no known workarounds. Users are encouraged to upgrade to a patched release.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | wasmtime | ≥ 19.0.0&&< 21.0.2 | 21.0.2 |
| 🦀crates.io | wasmtime | ≥ 22.0.0&&< 22.0.1 | 22.0.1 |
| 🦀crates.io | wasmtime | ≥ 23.0.0&&< 23.0.3 | 23.0.3 |
| 🦀crates.io | wasmtime | ≥ 24.0.0&&< 24.0.1 | 24.0.1 |
| 🦀crates.io | wasmtime | ≥ 25.0.0&&< 25.0.2 | 25.0.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for wasmtime. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update wasmtime to 21.0.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-47813 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2024-47813 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2024-47813. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2024-47813 in your dependencies?
O3 detects CVE-2024-47813 across crates.io dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.