GHSA-75hq-h6g9-h4q5 is a low-severity (CVSS 3.3) CWE-843 vulnerability in wasmtime. A fix is available for wasmtime — see the affected versions and patch details below.
Wasmtime vulnerable to panic when using a dropped extenref-typed element segment
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-75hq-h6g9-h4q5.
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-75hq-h6g9-h4q5 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 377,166 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
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
Impact
The 19.0.0 release of Wasmtime contains a regression introduced during its development which can lead to a guest WebAssembly module causing a panic in the host runtime. A valid WebAssembly module, when executed at runtime, may cause this panic. The panic in question is caused when a WebAssembly module issues a table.* instruction which uses a dropped element segment with a table that also has an externref type. This causes Wasmtime to erroneously use an empty function segment instead of an empty externref segment to perform this operation. This mismatch in types causes a panic in Wasmtime when it's asserted that an externref table is only viewed as externrefs.
This regression was introduced during the development of the 19.0.0 release and only affects the 19.0.0 release. This panic requires the reference-types WebAssembly feature to be enabled, and it is enabled by default. Toolchains are not known to generate this pattern by default so it's likely a module would need to be specifically crafted to trigger this panic.
A panic in a host runtime represents a possible denial-of-service in some scenarios. 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.
Patches
Wasmtime 19.0.1 has been released to fix this problem. Users of 19.0.0 should upgrade to 19.0.1. All other versions of Wasmtime are not affected by this issue.
Workarounds
If upgrading is not possible it's recommended to use config.reference_types(false). That will disable these modules at validation-time which prevents the possibility of a panic at runtime. If reference-types are required, however, then there is no other workaround at this time other than upgrading.
References
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | wasmtime | ≥ 19.0.0&&< 19.0.1 | 19.0.1cargo update -p wasmtime --precise 19.0.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for wasmtime, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update wasmtime to 19.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-75hq-h6g9-h4q5 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-75hq-h6g9-h4q5 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-75hq-h6g9-h4q5. 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-75hq-h6g9-h4q5 in your dependencies?
O3 Security finds GHSA-75hq-h6g9-h4q5 across crates.io dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.