medium6.5
CVE-2026-34942
Wasmtime: Panic when transcoding misaligned utf-16 strings
Impact
Wasmtime is a runtime for WebAssembly. Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, Wasmtime's implementation of transcoding strings into the Component Model's utf16 or latin1+utf16 encodings improperly verified the alignment of reallocated strings. This meant that unaligned pointers could be passed to the host for transcoding which would trigger a host panic. This panic is possible to trigger from malicious guests which transfer very specific strings across components with specific addresses. Host panics are considered a DoS vector in Wasmtime as the panic conditions are controlled by the guest in this situation. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| rust | wasmtime | < 24.0.7 | 24.0.7 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Bytecodealliance | Wasmtime | before 24.0.7 from 25.0.0 before 36.0.7 from 37.0.0 before 42.0.2 from 43.0.0 before 43.0.1 |