pysec-2021-321
Vulnerability from pysec
Wasmtime is an open source runtime for WebAssembly & WASI. In Wasmtime from version 0.26.0 and before version 0.30.0 is affected by a memory unsoundness vulnerability. There was an invalid free and out-of-bounds read and write bug when running Wasm that uses externrefs in Wasmtime. To trigger this bug, Wasmtime needs to be running Wasm that uses externrefs, the host creates non-null externrefs, Wasmtime performs a garbage collection (GC), and there has to be a Wasm frame on the stack that is at a GC safepoint where there are no live references at this safepoint, and there is a safepoint with live references earlier in this frame's function. Under this scenario, Wasmtime would incorrectly use the GC stack map for the safepoint from earlier in the function instead of the empty safepoint. This would result in Wasmtime treating arbitrary stack slots as externrefs that needed to be rooted for GC. At the next GC, it would be determined that nothing was referencing these bogus externrefs (because nothing could ever reference them, because they are not really externrefs) and then Wasmtime would deallocate them and run <ExternRef as Drop>::drop on them. This results in a free of memory that is not necessarily on the heap (and shouldn't be freed at this moment even if it was), as well as potential out-of-bounds reads and writes. Even though support for externrefs (via the reference types proposal) is enabled by default, unless you are creating non-null externrefs in your host code or explicitly triggering GCs, you cannot be affected by this bug. We have reason to believe that the effective impact of this bug is relatively small because usage of externref is currently quite rare. This bug has been patched and users should upgrade to Wasmtime version 0.30.0. If you cannot upgrade Wasmtime at this time, you can avoid this bug by disabling the reference types proposal by passing false to wasmtime::Config::wasm_reference_types.
{
"affected": [
{
"package": {
"ecosystem": "PyPI",
"name": "wasmtime",
"purl": "pkg:pypi/wasmtime"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "398a73f0dd862dbe703212ebae8e34036a18c11c"
}
],
"repo": "https://github.com/bytecodealliance/wasmtime",
"type": "GIT"
},
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.30.0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.0.1",
"0.0.2",
"0.11.0",
"0.12.0",
"0.15.0",
"0.15.1",
"0.16.0",
"0.16.1",
"0.17.0",
"0.18.0",
"0.18.1",
"0.18.2",
"0.19.0",
"0.20.0",
"0.21.0",
"0.22.0",
"0.23.0",
"0.24.0",
"0.25.0",
"0.26.0",
"0.27.0",
"0.28.0",
"0.28.1",
"0.29.0",
"0.9.0"
]
}
],
"aliases": [
"CVE-2021-39218",
"GHSA-4873-36h9-wv49"
],
"details": "Wasmtime is an open source runtime for WebAssembly \u0026 WASI. In Wasmtime from version 0.26.0 and before version 0.30.0 is affected by a memory unsoundness vulnerability. There was an invalid free and out-of-bounds read and write bug when running Wasm that uses `externref`s in Wasmtime. To trigger this bug, Wasmtime needs to be running Wasm that uses `externref`s, the host creates non-null `externrefs`, Wasmtime performs a garbage collection (GC), and there has to be a Wasm frame on the stack that is at a GC safepoint where there are no live references at this safepoint, and there is a safepoint with live references earlier in this frame\u0027s function. Under this scenario, Wasmtime would incorrectly use the GC stack map for the safepoint from earlier in the function instead of the empty safepoint. This would result in Wasmtime treating arbitrary stack slots as `externref`s that needed to be rooted for GC. At the *next* GC, it would be determined that nothing was referencing these bogus `externref`s (because nothing could ever reference them, because they are not really `externref`s) and then Wasmtime would deallocate them and run `\u003cExternRef as Drop\u003e::drop` on them. This results in a free of memory that is not necessarily on the heap (and shouldn\u0027t be freed at this moment even if it was), as well as potential out-of-bounds reads and writes. Even though support for `externref`s (via the reference types proposal) is enabled by default, unless you are creating non-null `externref`s in your host code or explicitly triggering GCs, you cannot be affected by this bug. We have reason to believe that the effective impact of this bug is relatively small because usage of `externref` is currently quite rare. This bug has been patched and users should upgrade to Wasmtime version 0.30.0. If you cannot upgrade Wasmtime at this time, you can avoid this bug by disabling the reference types proposal by passing `false` to `wasmtime::Config::wasm_reference_types`.",
"id": "PYSEC-2021-321",
"modified": "2021-09-17T22:30:49.898970Z",
"published": "2021-09-17T21:15:00Z",
"references": [
{
"type": "WEB",
"url": "https://crates.io/crates/wasmtime"
},
{
"type": "ADVISORY",
"url": "https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-4873-36h9-wv49"
},
{
"type": "FIX",
"url": "https://github.com/bytecodealliance/wasmtime/commit/398a73f0dd862dbe703212ebae8e34036a18c11c"
}
]
}
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.