Wasmtime: Bit-packing in Cranelift compiler causes silent overflow and miscompilation

{
  "id": "78cb8a33029b331cac6b476698a11032b7070bc665074f377c469d0f0b6fc39b",
  "url": "https://osv.dev/vulnerability/GHSA-897f-g5gm-fmxm",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Wasmtime: Bit-packing in Cranelift compiler causes silent overflow and miscompilation",
    "summary": "## Summary In Wasmtime prior to v43, the Cranelift compiler backend bit-packs its SSA value indices in a way that can result in silent overflow in release builds, and result in incorrect value references in the IR resulting in arbitrary miscompilation. A very large Wasm function body, or one that is specially crafted to use many SSA values, can use this to force type-confusion or other arbitrary side-effects and escape the sandbox. Cranelift was changed in Wasmtime v43 to use a full `u32` index, with checks if that limit is exceeded, and so is no longer susceptible to this bug. ## Impact A Wasmtime engine with default settings (using the Cranelift backend) on any architecture/platform could experience a sandbox escape from a specially-crafted Wasm module. ## Patches Wasmtime v36.0.19 has been released which fixes this issue.",
    "evidence": "osv:GHSA-897f-g5gm-fmxm",
    "products": [
      {
        "name": {
          "value": "wasmtime",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "36.0.19",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      },
      {
        "name": {
          "value": "wasmtime",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "43.0.0",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "critical",
    "structured": {
      "id": "GHSA-897f-g5gm-fmxm",
      "aliases": [
        "CVE-2026-115889",
        "GHSA-897f-g5gm-fmxm",
        "RUSTSEC-2026-0380"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "36.0.19"
                }
              ]
            }
          ],
          "package": {
            "name": "wasmtime",
            "purl": "pkg:cargo/wasmtime",
            "ecosystem": "crates.io"
          },
          "database_specific": {
            "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-897f-g5gm-fmxm/GHSA-897f-g5gm-fmxm.json"
          }
        },
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "37.0.0"
                },
                {
                  "fixed": "43.0.0"
                }
              ]
            }
          ],
          "package": {
            "name": "wasmtime",
            "purl": "pkg:cargo/wasmtime",
            "ecosystem": "crates.io"
          },
          "database_specific": {
            "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-897f-g5gm-fmxm/GHSA-897f-g5gm-fmxm.json"
          }
        }
      ],
      "modified": "2026-10-23T22:25:51.511659839Z",
      "provider": "osv",
      "references": [
        "https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-897f-g5gm-fmxm",
        "https://github.com/bytecodealliance/wasmtime/pull/12613",
        "https://github.com/bytecodealliance/wasmtime/pull/14818",
        "https://github.com/bytecodealliance/wasmtime/commit/ba8f7d70caa1825b7f64fa75cd9d03f4a438dae0",
        "https://github.com/bytecodealliance/wasmtime/commit/f517bd6e890c7c1291ab9fe05d8cc0c9f11e56aa",
        "https://github.com/bytecodealliance/wasmtime",
        "https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.19",
        "https://github.com/bytecodealliance/wasmtime/releases/tag/v43.0.0",
        "https://rustsec.org/advisories/RUSTSEC-2026-0380.html"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-197",
          "CWE-843"
        ],
        "severity": "CRITICAL",
        "github_reviewed": true,
        "nvd_published_at": null,
        "github_reviewed_at": "2026-10-23T22:02:20Z"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-115889",
        "evidence": "/aliases"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/database_specific/severity"
  },
  "source_id": "core-osv",
  "document_id": 427060,
  "published_at": "2026-10-23T22:02:20+00:00"
}