CVE-2022-39394: wasmtime_trap_code C API function has out of bounds write vulnerability

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2022-11-10 · updated 2026-06-17
Weakness: CWE-787

Description

Wasmtime is a standalone runtime for WebAssembly. Prior to version 2.0.2, there is a bug in Wasmtime's C API implementation where the definition of the `wasmtime_trap_code` does not match its declared signature in the `wasmtime/trap.h` header file. This discrepancy causes the function implementation to perform a 4-byte write into a 1-byte buffer provided by the caller. This can lead to three zero bytes being written beyond the 1-byte location provided by the caller. This bug has been patched and users should upgrade to Wasmtime 2.0.2. This bug can be worked around by providing a 4-byte buffer casted to a 1-byte buffer when calling `wasmtime_trap_code`. Users of the `wasmtime` crate are not affected by this issue, only users of the C API function `wasmtime_trap_code` are affected.

Affected products

bytecodealliance wasmtime: before 1.0.2; from 2.0.0 before 2.0.2 — fixed in 1.0.2, 2.0.2

How to fix

Upgrade to a fixed version: bytecodealliance wasmtime 1.0.2, 2.0.2. Check the vendor advisory for mitigations.

References

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