CVE-2022-23636: Wasmtime is an open source runtime for WebAssembly & WASI. Prior to versions 0.34.1 and 0.33.1, there exists a bug in the pooling instance allocator i...

Description

Wasmtime is an open source runtime for WebAssembly & WASI. Prior to versions 0.34.1 and 0.33.1, there exists a bug in the pooling instance allocator in Wasmtime's runtime where a failure to instantiate an instance for a module that defines an `externref` global will result in an invalid drop of a `VMExternRef` via an uninitialized pointer. A number of conditions listed in the GitHub Security Advisory must be true in order for an instance to be vulnerable to this issue. Maintainers believe that the effective impact of this bug is relatively small because the usage of `externref` is still uncommon and without a resource limiter configured on the `Store`, which is not the default configuration, it is only possible to trigger the bug from an error returned by `mprotect` or `VirtualAlloc`. Note that on Linux with the `uffd` feature enabled, it is only possible to trigger the bug from a resource limiter as the call to `mprotect` is skipped. The bug has been fixed in 0.34.1 and 0.33.1 and users are encouraged to upgrade as soon as possible. If it is not possible to upgrade to version 0.34.1 or 0.33.1 of the `wasmtime` crate, it is recommend that support for the reference types proposal be disabled by passing `false` to `Config::wasm_reference_types`. Doing so will prevent modules that use `externref` from being loaded entirely.

Metrics

CVSS 3.1

8.1/10

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

0.76%

50.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-824

Affected Software

Vendor	Product	Versions
Bytecodealliance	Wasmtime	< 0.33.1
Bytecodealliance	Wasmtime	0.34.0

References

https://github.com/bytecodealliance/wasmtime/commit/886ecc562040bef61faf19438c22285c2d62403aPatch, Third Party Advisory
https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-88xq-w8cq-xfg7Mitigation, Third Party Advisory
https://github.com/bytecodealliance/wasmtime/commit/886ecc562040bef61faf19438c22285c2d62403aPatch, Third Party Advisory
https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-88xq-w8cq-xfg7Mitigation, Third Party Advisory

Timeline

Published: Feb 16, 2022
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2022-23636?

Wasmtime is an open source runtime for WebAssembly & WASI. Prior to versions 0.34.1 and 0.33.1, there exists a bug in the pooling instance allocator in Wasmtime's runtime where a failure to instantiate an instance for a module that defines an `externref` global will result in an invalid drop of a `VMExternRef` via an uninitialized pointer. A number of conditions listed in the GitHub Security Advisory must be true in order for an instance to be vulnerable to this issue. Maintainers believe that the effective impact of this bug is relatively small because the usage of `externref` is still uncommon and without a resource limiter configured on the `Store`, which is not the default configuration, it is only possible to trigger the bug from an error returned by `mprotect` or `VirtualAlloc`. Note that on Linux with the `uffd` feature enabled, it is only possible to trigger the bug from a resource limiter as the call to `mprotect` is skipped. The bug has been fixed in 0.34.1 and 0.33.1 and users are encouraged to upgrade as soon as possible. If it is not possible to upgrade to version 0.34.1 or 0.33.1 of the `wasmtime` crate, it is recommend that support for the reference types proposal be disabled by passing `false` to `Config::wasm_reference_types`. Doing so will prevent modules that use `externref` from being loaded entirely.

How severe is CVE-2022-23636?

CVE-2022-23636 has a CVSS score of 8.1/10 (HIGH severity). The EPSS model estimates a 0.76% probability of exploitation in the next 30 days.

How do I fix CVE-2022-23636?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.