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CVE-2021-39219— Wrong type for `Linker`-define functions when used across two `Engine`s

Quick assessment

Affected
bytecodealliance wasmtime
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Wasmtime是一个字节码联盟项目，它是一个独立的仅用于 WebAssembly 和 WASI 的 wasm 优化运行时。 Wasmtime 存在代码问题漏洞，该漏洞源于 0.30.0 版本之前的 Wasmtime 受类型混淆漏洞影响。

CVSS 6.3 · Medium EPSS 0.36% · P28

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2021-39219

Vulnerability Information
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Vulnerability Title
Wrong type for `Linker`-define functions when used across two `Engine`s
Source: CVE Program / CVE List V5
Vulnerability Description
Wasmtime is an open source runtime for WebAssembly & WASI. Wasmtime before version 0.30.0 is affected by a type confusion vulnerability. As a Rust library the `wasmtime` crate clearly marks which functions are safe and which are `unsafe`, guaranteeing that if consumers never use `unsafe` then it should not be possible to have memory unsafety issues in their embeddings of Wasmtime. An issue was discovered in the safe API of `Linker::func_*` APIs. These APIs were previously not sound when one `Engine` was used to create the `Linker` and then a different `Engine` was used to create a `Store` and then the `Linker` was used to instantiate a module into that `Store`. Cross-`Engine` usage of functions is not supported in Wasmtime and this can result in type confusion of function pointers, resulting in being able to safely call a function with the wrong type. Triggering this bug requires using at least two `Engine` values in an embedding and then additionally using two different values with a `Linker` (one at the creation time of the `Linker` and another when instantiating a module with the `Linker`). It's expected that usage of more-than-one `Engine` in an embedding is relatively rare since an `Engine` is intended to be a globally shared resource, so the expectation is that the impact of this issue is relatively small. The fix implemented is to change this behavior to `panic!()` in Rust instead of silently allowing it. Using different `Engine` instances with a `Linker` is a programmer bug that `wasmtime` catches at runtime. This bug has been patched and users should upgrade to Wasmtime version 0.30.0. If you cannot upgrade Wasmtime and are using more than one `Engine` in your embedding it's recommended to instead use only one `Engine` for the entire program if possible. An `Engine` is designed to be a globally shared resource that is suitable to have only one for the lifetime of an entire process. If using multiple `Engine`s is required then code should be audited to ensure that `Linker` is only used with one `Engine`.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
使用不兼容类型访问资源(类型混淆)
Source: CVE Program / CVE List V5
Vulnerability Title
Wasmtime 代码问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Wasmtime是一个字节码联盟项目，它是一个独立的仅用于 WebAssembly 和 WASI 的 wasm 优化运行时。 Wasmtime 存在代码问题漏洞，该漏洞源于 0.30.0 版本之前的 Wasmtime 受类型混淆漏洞影响。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
bytecodealliance wasmtime <= 0.29.0 -

II. Public POCs for CVE-2021-39219

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III. Intelligence Information for CVE-2021-39219

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Patches & Fixes for CVE-2021-39219 (1)

Vendor Advisories for CVE-2021-39219 (1)

Mailing List Discussions for CVE-2021-39219 (2)

Other References for CVE-2021-39219 (1)

Same Patch Batch · bytecodealliance · 2021-09-17 · 3 CVEs total

CVE-2021-39216 6.3 MEDIUM Use after free passing `externref`s to Wasm in Wasmtime
CVE-2021-39218 6.3 MEDIUM Out-of-bounds read/write and invalid free with `externref`s and GC safepoints in Wasmtime

IV. Related Vulnerabilities

Same product: wasmtime
Same vendor: bytecodealliance
Same weakness: CWE-843

V. Comments for CVE-2021-39219

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