CVE-2022-39392: Wasmtime is a standalone runtime for WebAssembly. Prior to version 2.0.2, there is a bug in Wasmtime's implementation of its pooling instance allocato...

Description

Wasmtime is a standalone runtime for WebAssembly. Prior to version 2.0.2, there is a bug in Wasmtime's implementation of its pooling instance allocator when the allocator is configured to give WebAssembly instances a maximum of zero pages of memory. In this configuration, the virtual memory mapping for WebAssembly memories did not meet the compiler-required configuration requirements for safely executing WebAssembly modules. Wasmtime's default settings require virtual memory page faults to indicate that wasm reads/writes are out-of-bounds, but the pooling allocator's configuration would not create an appropriate virtual memory mapping for this meaning out of bounds reads/writes can successfully read/write memory unrelated to the wasm sandbox within range of the base address of the memory mapping created by the pooling allocator. This bug is not applicable with the default settings of the `wasmtime` crate. This bug can only be triggered by setting `InstanceLimits::memory_pages` to zero. This is expected to be a very rare configuration since this means that wasm modules cannot allocate any pages of linear memory. All wasm modules produced by all current toolchains are highly likely to use linear memory, so it's expected to be unlikely that this configuration is set to zero by any production embedding of Wasmtime. This bug has been patched and users should upgrade to Wasmtime 2.0.2. This bug can be worked around by increasing the `memory_pages` allotment when configuring the pooling allocator to a value greater than zero. If an embedding wishes to still prevent memory from actually being used then the `Store::limiter` method can be used to dynamically disallow growth of memory beyond 0 bytes large. Note that the default `memory_pages` value is greater than zero.

Metrics

CVSS 3.1

7.4/10

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

EPSS Probability

0.58%

43.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Bytecodealliance	Wasmtime	< 1.0.2
Bytecodealliance	Wasmtime	>= 2.0.0, < 2.0.2

References

https://github.com/bytecodealliance/wasmtime/commit/e60c3742904ccbb3e26da201c9221c38a4981d72Patch, Third Party Advisory
https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-44mr-8vmm-wjhgThird Party Advisory
https://github.com/bytecodealliance/wasmtime/commit/e60c3742904ccbb3e26da201c9221c38a4981d72Patch, Third Party Advisory
https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-44mr-8vmm-wjhgThird Party Advisory

Timeline

Published: Nov 10, 2022
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2022-39392?

Wasmtime is a standalone runtime for WebAssembly. Prior to version 2.0.2, there is a bug in Wasmtime's implementation of its pooling instance allocator when the allocator is configured to give WebAssembly instances a maximum of zero pages of memory. In this configuration, the virtual memory mapping for WebAssembly memories did not meet the compiler-required configuration requirements for safely executing WebAssembly modules. Wasmtime's default settings require virtual memory page faults to indicate that wasm reads/writes are out-of-bounds, but the pooling allocator's configuration would not create an appropriate virtual memory mapping for this meaning out of bounds reads/writes can successfully read/write memory unrelated to the wasm sandbox within range of the base address of the memory mapping created by the pooling allocator. This bug is not applicable with the default settings of the `wasmtime` crate. This bug can only be triggered by setting `InstanceLimits::memory_pages` to zero. This is expected to be a very rare configuration since this means that wasm modules cannot allocate any pages of linear memory. All wasm modules produced by all current toolchains are highly likely to use linear memory, so it's expected to be unlikely that this configuration is set to zero by any production embedding of Wasmtime. This bug has been patched and users should upgrade to Wasmtime 2.0.2. This bug can be worked around by increasing the `memory_pages` allotment when configuring the pooling allocator to a value greater than zero. If an embedding wishes to still prevent memory from actually being used then the `Store::limiter` method can be used to dynamically disallow growth of memory beyond 0 bytes large. Note that the default `memory_pages` value is greater than zero.

How severe is CVE-2022-39392?

CVE-2022-39392 has a CVSS score of 7.4/10 (HIGH severity). The EPSS model estimates a 0.58% probability of exploitation in the next 30 days.

How do I fix CVE-2022-39392?

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.