{
  "affected": [
    {
      "package": {
        "ecosystem": "crates.io",
        "name": "wasmtime"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "43.0.0"
            },
            {
              "fixed": "43.0.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "43.0.0"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-34983"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-416"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-09T20:23:44Z",
    "nvd_published_at": "2026-04-09T19:16:24Z",
    "severity": "LOW"
  },
  "details": "### Impact\n\nIn version 43.0.0 of the `wasmtime` crate, cloning a `wasmtime::Linker` is unsound and can result in use-after-free bugs.\n\nThis bug is not controllable by guest Wasm programs. It can only be triggered by a specific sequence of embedder API calls made by the host.\n\nThe typical symptom of this use-after-free bug is a segfault. It does not enable heap corruption or data leakage.\n\nIf you are using the `wasmtime` CLI, rather than the embedding API, you are not affected. If you are using the embedding API but are not calling `wasmtime::Linker`\u0027s `Clone` implementation, you are not affected.\n\nSpecifically, the following steps must occur to trigger the bug:\n\n* Clone a `wasmtime::Linker`\n* Drop the original linker instance\n* Use the new, cloned linker instance, resulting in a use-after-free\n\n### Patches\n\nThis bug has been patched in Wasmtime version 43.0.1\n\n### Workarounds\n\nWasmtime embedders are highly encouraged to upgrade their `wasmtime` crate dependency.\n\nIf upgrading is not an option, or as a temporary workaround before upgrading, you can avoid this bug by not cloning `wasmtime::Linker` and instead creating a new, empty `wasmtime::Linker` and manually reregistering the host APIs from the original linker:\n\n```rust\nuse wasmtime::{Linker, Result, Store};\n\nfn clone_linker\u003cT\u003e(linker: \u0026Linker\u003cT\u003e, store: \u0026mut Store\u003cT\u003e) -\u003e Result\u003cLinker\u003cT\u003e\u003e {\n    let mut cloned = Linker::new();\n    for (module, name, item) in linker.iter(store) {\n        cloned.define(module, name, item)?;\n    }\n    Ok(cloned)\n}\n```\n\n### References\n\nThis bug was introduced during an internal refactoring that was part of our efforts to [robustly handle allocation failure in Wasmtime](https://github.com/bytecodealliance/wasmtime/issues/12069). This refactoring introduced an string-interning pool which had an unsound `TryClone`[^try-clone] implementation.\n\n[^try-clone]: [The `TryClone` trait](https://github.com/bytecodealliance/wasmtime/blob/33e8b3d955697587b23cf39d87fbcbdb4d26b0c9/crates/core/src/alloc/try_clone.rs#L5-L17) is our version of the Rust standard library\u0027s `Clone` trait that allows for returning `OutOfMemory` errors.\n\n* The `StringPool` was introduced in https://github.com/bytecodealliance/wasmtime/pull/12536, at which time the bug in `TryClone for StringPool` was already present, although this code path was not yet used anywhere.\n* `wasmtime::Linker` was refactored to internally use `StringPool` in https://github.com/bytecodealliance/wasmtime/pull/12537, at which time the buggy code path became accessible.\n* This bug was originally reported to the Wasmtime maintainers as https://github.com/bytecodealliance/wasmtime/pull/12906",
  "id": "GHSA-hfr4-7c6c-48w2",
  "modified": "2026-04-10T14:39:54Z",
  "published": "2026-04-09T20:23:44Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-hfr4-7c6c-48w2"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-34983"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/bytecodealliance/wasmtime"
    },
    {
      "type": "WEB",
      "url": "https://rustsec.org/advisories/RUSTSEC-2026-0090.html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:P/AC:H/AT:P/PR:H/UI:A/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Wasmtime has use-after-free bug after cloning `wasmtime::Linker`"
}