rust-wasmtime — security advisory

{
  "id": "1622e51440b2df28e042a9d91fbabeb064da6d1b40b21c72cbfc5750dba76887",
  "url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-34987",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "UBUNTU-CVE-2026-34987",
    "summary": "Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime with its Winch (baseline) non-default compiler backend may allow properly constructed guest Wasm to access host memory outside of its linear-memory sandbox. This vulnerability requires use of the Winch compiler (-Ccompiler=winch). By default, Wasmtime uses its Cranelift backend, not Winch. With Winch, the same incorrect assumption is present in theory on both aarch64 and x86-64. The aarch64 case has an observed-working proof of concept, while the x86-64 case is theoretical and may not be reachable in practice. This Winch compiler bug can allow the Wasm guest to access memory before or after the linear-memory region, independently of whether pre- or post-guard regions are configured. The accessible range in the initial bug proof-of-concept is up to 32KiB before the start of memory, or ~4GiB after the start of memory, independently of the size of pre- or post-guard regions or the use of explicit or guard-region-based bounds checking. However, the underlying bug assumes a 32-bit memory offset stored in a 64-bit register has its upper bits cleared when it may not, and so closely related variants of the initial proof-of-concept may be able to access truly arbitrary memory in-process. This could result in a host process segmentation fault (DoS), an arbitrary data leak from the host process, or with a write, potentially an arbitrary RCE. This vulnerability is fixed in 36.0.7, 42.0.2, an",
    "evidence": "osv:UBUNTU-CVE-2026-34987",
    "products": [
      {
        "name": {
          "value": "rust-wasmtime",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "10.0.1+dfsg-7",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "15.0.1+dfsg-4",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "16.0.0+dfsg-2",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "16.0.0+dfsg-3",
            "evidence": "/affected/0/versions"
          }
        ]
      },
      {
        "name": {
          "value": "rust-wasmtime",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "26.0.1+dfsg-3",
            "evidence": "/affected/1/versions"
          }
        ]
      },
      {
        "name": {
          "value": "rust-wasmtime",
          "evidence": "/affected/2/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "36.0.5+dfsg-1",
            "evidence": "/affected/2/versions"
          },
          {
            "value": "36.0.13+dfsg-1",
            "evidence": "/affected/2/versions"
          }
        ]
      },
      {
        "name": {
          "value": "rust-wasmtime",
          "evidence": "/affected/3/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "26.0.1+dfsg-3",
            "evidence": "/affected/3/versions"
          },
          {
            "value": "26.0.1+dfsg-4",
            "evidence": "/affected/3/versions"
          },
          {
            "value": "28.0.1+dfsg-3",
            "evidence": "/affected/3/versions"
          },
          {
            "value": "29.0.1+dfsg-5",
            "evidence": "/affected/3/versions"
          },
          {
            "value": "36.0.5+dfsg-1",
            "evidence": "/affected/3/versions"
          }
        ]
      }
    ],
    "severity": "critical",
    "structured": {
      "id": "UBUNTU-CVE-2026-34987",
      "aliases": [
        "UBUNTU-CVE-2026-34987"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H"
        },
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H"
        },
        {
          "type": "Ubuntu",
          "score": "medium"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                }
              ]
            }
          ],
          "package": {
            "name": "rust-wasmtime",
            "purl": "pkg:deb/ubuntu/rust-wasmtime?arch=source&distro=noble",
            "ecosystem": "Ubuntu:24.04:LTS"
          },
          "versions": [
            "10.0.1+dfsg-7",
            "15.0.1+dfsg-4",
            "16.0.0+dfsg-2",
            "16.0.0+dfsg-3"
          ],
          "database_specific": {
            "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-34987.json"
          },
          "ecosystem_specific": {
            "binaries": [
              {
                "binary_name": "librust-cranelift-dev",
                "binary_version": "0.103.0+16.0.0+dfsg-3"
              }
            ]
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                }
              ]
            }
          ],
          "package": {
            "name": "rust-wasmtime",
            "purl": "pkg:deb/ubuntu/rust-wasmtime?arch=source&distro=questing",
            "ecosystem": "Ubuntu:25.10"
          },
          "versions": [
            "26.0.1+dfsg-3"
          ],
          "database_specific": {
            "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-34987.json"
          },
          "ecosystem_specific": {
            "binaries": [
              {
                "binary_name": "librust-cranelift-dev",
                "binary_version": "0.113.1+26.0.1+dfsg-3"
              }
            ]
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                }
              ]
            }
          ],
          "package": {
            "name": "rust-wasmtime",
            "purl": "pkg:deb/ubuntu/rust-wasmtime?arch=source&distro=stonking",
            "ecosystem": "Ubuntu:26.10"
          },
          "versions": [
            "36.0.5+dfsg-1",
            "36.0.13+dfsg-1"
          ],
          "database_specific": {
            "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-34987.json"
          },
          "ecosystem_specific": {
            "binaries": [
              {
                "binary_name": "librust-cranelift-dev",
                "binary_version": "0.123.13+36.0.13+dfsg-1"
              }
            ]
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                }
              ]
            }
          ],
          "package": {
            "name": "rust-wasmtime",
            "purl": "pkg:deb/ubuntu/rust-wasmtime?arch=source&distro=resolute",
            "ecosystem": "Ubuntu:26.04:LTS"
          },
          "versions": [
            "26.0.1+dfsg-3",
            "26.0.1+dfsg-4",
            "28.0.1+dfsg-3",
            "29.0.1+dfsg-5",
            "36.0.5+dfsg-1"
          ],
          "database_specific": {
            "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-34987.json"
          },
          "ecosystem_specific": {
            "binaries": [
              {
                "binary_name": "librust-cranelift-dev",
                "binary_version": "0.123.5+36.0.5+dfsg-1"
              }
            ]
          }
        }
      ],
      "modified": "2026-10-17T13:00:02.321323398Z",
      "provider": "osv",
      "upstream": [
        "CVE-2026-34987"
      ],
      "references": [
        "https://ubuntu.com/security/CVE-2026-34987",
        "https://www.cve.org/CVERecord?id=CVE-2026-34987",
        "https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-xx5w-cvp6-jv83"
      ]
    },
    "related_cves": [
      {
        "value": "CVE-2026-34987",
        "evidence": "/upstream"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/1/score"
  },
  "source_id": "core-osv",
  "document_id": 360168,
  "published_at": "2026-04-09T19:16:00+00:00"
}