CVE-2025-53901
LOWWasmtime has host panic with `fd_renumber` WASIp1 function
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-wasi🦀wasmtime-wasi🦀wasmtime-wasi🦀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 a runtime for WebAssembly. Prior to versions 24.0.4, 33.0.2, and 34.0.2, a bug in Wasmtime's implementation of the WASIp1 set of import functions can lead to a WebAssembly guest inducing a panic in the host (embedder). The specific bug is triggered by calling path_open after calling fd_renumber with either two equal argument values or a second argument being equal to a previously-closed file descriptor number value. The corrupt state introduced in fd_renumber will lead to the subsequent opening of a file descriptor to panic. This panic cannot introduce memory unsafety or allow WebAssembly to break outside of its sandbox, however. There is no possible heap corruption or memory unsafety from this panic. This bug is in the implementation of Wasmtime's wasmtime-wasi crate which provides an implementation of WASIp1. The bug requires a specially crafted call to fd_renumber in addition to the ability to open a subsequent file descriptor. Opening a second file descriptor is only possible when a preopened directory was provided to the guest, and this is common amongst embeddings. A panic in the host is considered a denial-of-service vector for WebAssembly embedders and is thus a security issue in Wasmtime. This bug does not affect WASIp2 and embedders using components. In accordance with Wasmtime's release process, patch releases are available as 24.0.4, 33.0.2, and 34.0.2. Users of other release of Wasmtime are recommended to move to a supported release of Wasmtime. Embedders who are using components or are not providing guest access to create more file descriptors (e.g. via a preopened filesystem directory) are not affected by this issue. Otherwise, there is no workaround at this time, and affected embeddings are recommended to update to a patched version which will not cause a panic in the host.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | wasmtime-wasi | all versions | 24.0.4 |
| 🦀crates.io | wasmtime-wasi | ≥ 25.0.0&&< 33.0.2 | 33.0.2 |
| 🦀crates.io | wasmtime-wasi | ≥ 34.0.0&&< 34.0.2 | 34.0.2 |
| 🦀crates.io | wasmtime | ≥ 10.0.0&&< 24.0.4 | 24.0.4 |
| 🦀crates.io | wasmtime | ≥ 33.0.0&&< 33.0.2 | 33.0.2 |
| 🦀crates.io | wasmtime | ≥ 34.0.0&&< 34.0.2 | 34.0.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for wasmtime-wasi. 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-wasi to 24.0.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-53901 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-2025-53901 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-2025-53901. 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-2025-53901 in your dependencies?
O3 detects CVE-2025-53901 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.