CVSS3
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
HIGH
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
LOW
Availability Impact
NONE
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:L/A:N
AI Score
Confidence
Low
SSVC
Exploitation
none
Automatable
no
Technical Impact
partial
Wasmtime is a standalone runtime for WebAssembly. Wasmtime versions from 10.0.0 to versions 10.02, 11.0.2, and 12.0.1 contain a miscompilation of the WebAssembly i64x2.shr_s
instruction on x86_64 platforms when the shift amount is a constant value that is larger than 32. Only x86_64 is affected so all other targets are not affected by this. The miscompilation results in the instruction producing an incorrect result, namely the low 32-bits of the second lane of the vector are derived from the low 32-bits of the second lane of the input vector instead of the high 32-bits. The primary impact of this issue is that any WebAssembly program using the i64x2.shr_s
with a constant shift amount larger than 32 may produce an incorrect result.
This issue is not an escape from the WebAssembly sandbox. Execution of WebAssembly guest programs will still behave correctly with respect to memory sandboxing and isolation from the host. Wasmtime considers non-spec-compliant behavior as a security issue nonetheless.
This issue was discovered through fuzzing of Wasmtime’s code generator Cranelift.
Wasmtime versions 10.0.2, 11.0.2, and 12.0.2 are all patched to no longer have this miscompilation. This issue only affects x86_64 hosts and the only workaround is to either scan for this pattern in wasm modules which is nontrivial or to disable the SIMD proposal for WebAssembly. Users prior to 10.0.0 are unaffected by this vulnerability.
docs.rs/wasmtime/latest/wasmtime/struct.Config.html#method.wasm_simd
github.com/bytecodealliance/wasmtime/commit/8d7eda15b0badcbea83a7aac2d08f80788b59240
github.com/bytecodealliance/wasmtime/pull/6372
github.com/bytecodealliance/wasmtime/security/advisories/GHSA-gw5p-q8mj-p7gh
github.com/bytecodealliance/wasmtime/security/advisories/GHSA-gw5p-q8mj-p7gh#:~:text=Mailing%20list%20announcement
CVSS3
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
HIGH
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
LOW
Availability Impact
NONE
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:L/A:N
AI Score
Confidence
Low
SSVC
Exploitation
none
Automatable
no
Technical Impact
partial