GHSA-fm79-3f68-h2fc is a low-severity (CVSS 3.5) CWE-672 vulnerability in wasmtime-wasi. A fix is available for wasmtime-wasi — see the affected versions and patch details below.
Wasmtime CLI is vulnerable to host panic through its fd_renumber function
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-fm79-3f68-h2fc.
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.
How urgent is this, really
GHSA-fm79-3f68-h2fc plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 379,145 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
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
Summary
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
- 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.
Patches
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.
Workarounds
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 | 24.0.4cargo update -p wasmtime-wasi --precise 24.0.4 |
| 🦀crates.io | wasmtime-wasi | ≥ 25.0.0&&< 33.0.2 | 33.0.2cargo update -p wasmtime-wasi --precise 33.0.2 |
| 🦀crates.io | wasmtime-wasi | ≥ 34.0.0&&< 34.0.2 | 34.0.2cargo update -p wasmtime-wasi --precise 34.0.2 |
| 🦀crates.io | wasmtime | ≥ 10.0.0&&< 24.0.4 | 24.0.4cargo update -p wasmtime --precise 24.0.4 |
| 🦀crates.io | wasmtime | ≥ 33.0.0&&< 33.0.2 | 33.0.2cargo update -p wasmtime --precise 33.0.2 |
| 🦀crates.io | wasmtime | ≥ 34.0.0&&< 34.0.2 | 34.0.2cargo update -p wasmtime --precise 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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update wasmtime-wasi to 24.0.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-fm79-3f68-h2fc 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-fm79-3f68-h2fc can be triaged on real exposure rather than presence alone.
Tailored to GHSA-fm79-3f68-h2fc. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-fm79-3f68-h2fc in your dependencies?
O3 Security finds GHSA-fm79-3f68-h2fc across crates.io dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.