CVE-2022-31146

Published: 21 July 2022

Wasmtime is a standalone runtime for WebAssembly. There is a bug in the Wasmtime's code generator, Cranelift, where functions using reference types may be incorrectly missing metadata required for runtime garbage collection. This means that if a GC happens at runtime then the GC pass will mistakenly think these functions do not have live references to GC'd values, reclaiming them and deallocating them. The function will then subsequently continue to use the values assuming they had not been GC'd, leading later to a use-after-free. This bug was introduced in the migration to the `regalloc2` register allocator that occurred in the Wasmtime 0.37.0 release on 2022-05-20. This bug has been patched and users should upgrade to Wasmtime version 0.38.2. Mitigations for this issue can be achieved by disabling the reference types proposal by passing `false` to `wasmtime::Config::wasm_reference_types` or downgrading to Wasmtime 0.36.0 or prior.

Notes

mozjs contains a copy of the SpiderMonkey JavaScript engine

starting with Ubuntu 22.04, the firefox package is just a script
that installs the Firefox snap

cranelift, the wasmtime code generator is included in
firefox, thunderbird and mozjs families.

Status

Severity score breakdown

References

• https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-5fhj-g3p3-pq9g
• https://github.com/WebAssembly/reference-types
• https://github.com/bytecodealliance/wasmtime/
• https://github.com/bytecodealliance/wasmtime/commit/2154c63de94e0372bca5a596c3eaf90147c922d1
• https://www.cve.org/CVERecord?id=CVE-2022-31146
• NVD
• Launchpad
• Debian