Bug 2006105 (CVE-2021-39219)

Summary: CVE-2021-39219 wasmtime: Type confusion vulnerability
Product: [Other] Security Response Reporter: Pedro Sampaio <psampaio>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED UPSTREAM QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: o.lemasle, rust-sig
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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Last Closed: 2021-09-21 00:21:13 UTC Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On: 2006107, 2006108, 2006109    
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Description Pedro Sampaio 2021-09-20 21:15:52 UTC
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`.

https://crates.io/crates/wasmtime
https://github.com/bytecodealliance/wasmtime/commit/b39f087414f27ae40c44449ed5d1154e03449bff
https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-q879-9g95-56mx

Comment 1 Pedro Sampaio 2021-09-20 21:16:42 UTC
Created rust-wasmtime-cache tracking bugs for this issue:

Affects: fedora-34 [bug 2006107]


Created rust-wasmtime-environ tracking bugs for this issue:

Affects: fedora-34 [bug 2006108]


Created rust-wasmtime-fiber tracking bugs for this issue:

Affects: fedora-34 [bug 2006109]

Comment 2 Product Security DevOps Team 2021-09-21 00:21:13 UTC
This CVE Bugzilla entry is for community support informational purposes only as it does not affect a package in a commercially supported Red Hat product. Refer to the dependent bugs for status of those individual community products.