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rust-wasmtime — security advisory

Type: advisorySources: OSVAdvisory ID: UBUNTU-CVE-2026-35195

Wasmtime is a runtime for WebAssembly. Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, Wasmtime's implementation of transcoding strings between components contains a bug where the return value of a guest component's realloc is not validated before the host attempts to write through the pointer. This enables a guest to cause the host to write arbitrary transcoded string bytes to an arbitrary location up to 4GiB away from the base of linear memory. These writes on the host could hit unmapped memory or could corrupt host data structures depending on Wasmtime's configuration. Wasmtime by default reserves 4GiB of virtual memory for a guest's linear memory meaning that this bug will by default on hosts cause the host to hit unmapped memory and abort the process due to an unhandled fault. Wasmtime can be configured, however, to reserve less memory for a guest and to remove all guard pages, so some configurations of Wasmtime may lead to corruption of data outside of a guest's linear memory, such as host data structures or other guests's linear memories. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1.

Products
rust-wasmtime
Affected versions
10.0.1+dfsg-7, 15.0.1+dfsg-4, 16.0.0+dfsg-2, 16.0.0+dfsg-3, 26.0.1+dfsg-3, 26.0.1+dfsg-4, 28.0.1+dfsg-3, 29.0.1+dfsg-5, 36.0.13+dfsg-1, 36.0.5+dfsg-1
Fixed versions
Not specified
CVEs
CVE-2026-35195
Confirmed fixed CVEs
Not specified
Updated in this feed
31 Oct 2026, 02:10 UTC · Revision 1

Source evidence

UBUNTU-CVE-2026-35195

core-osv · Original source

Published 9 Apr 2026, 19:16 UTC

Wasmtime is a runtime for WebAssembly. Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, Wasmtime's implementation of transcoding strings between components contains a bug where the return value of a guest component's realloc is not validated before the host attempts to write through the pointer. This enables a guest to cause the host to write arbitrary transcoded string bytes to an arbitrary location up to 4GiB away from the base of linear memory. These writes on the host could hit unmapped memory or could corrupt host data structures depending on Wasmtime's configuration. Wasmtime by default reserves 4GiB of virtual memory for a guest's linear memory meaning that this bug will by default on hosts cause the host to hit unmapped memory and abort the process due to an unhandled fault. Wasmtime can be configured, however, to reserve less memory for a guest and to remove all guard pages, so some configurations of Wasmtime may lead to corruption of data outside of a guest's linear memory, such as host data structures or other guests's linear memories. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1.

osv:UBUNTU-CVE-2026-35195

rust-wasmtime

Fixed versions: Not specified

rust-wasmtime

Fixed versions: Not specified

rust-wasmtime

Fixed versions: Not specified

rust-wasmtime

Fixed versions: Not specified

Complete source record
{
  "id": "b6a812d39afcf2df27ab2886e94553a82f02bac8a99b8530a8d3a2284fb1c36a",
  "url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-35195",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "UBUNTU-CVE-2026-35195",
    "summary": "Wasmtime is a runtime for WebAssembly. Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, Wasmtime's implementation of transcoding strings between components contains a bug where the return value of a guest component's realloc is not validated before the host attempts to write through the pointer. This enables a guest to cause the host to write arbitrary transcoded string bytes to an arbitrary location up to 4GiB away from the base of linear memory. These writes on the host could hit unmapped memory or could corrupt host data structures depending on Wasmtime's configuration. Wasmtime by default reserves 4GiB of virtual memory for a guest's linear memory meaning that this bug will by default on hosts cause the host to hit unmapped memory and abort the process due to an unhandled fault. Wasmtime can be configured, however, to reserve less memory for a guest and to remove all guard pages, so some configurations of Wasmtime may lead to corruption of data outside of a guest's linear memory, such as host data structures or other guests's linear memories. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1.",
    "evidence": "osv:UBUNTU-CVE-2026-35195",
    "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": "medium",
    "structured": {
      "id": "UBUNTU-CVE-2026-35195",
      "aliases": [
        "UBUNTU-CVE-2026-35195"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N"
        },
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N"
        },
        {
          "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-2026-35195.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-2026-35195.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-2026-35195.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-2026-35195.json"
          },
          "ecosystem_specific": {
            "binaries": [
              {
                "binary_name": "librust-cranelift-dev",
                "binary_version": "0.123.5+36.0.5+dfsg-1"
              }
            ]
          }
        }
      ],
      "modified": "2026-10-17T12:58:13.152396408Z",
      "provider": "osv",
      "upstream": [
        "CVE-2026-35195"
      ],
      "references": [
        "https://ubuntu.com/security/CVE-2026-35195",
        "https://www.cve.org/CVERecord?id=CVE-2026-35195",
        "https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-394w-hwhg-8vgm"
      ]
    },
    "related_cves": [
      {
        "value": "CVE-2026-35195",
        "evidence": "/upstream"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 358362,
  "published_at": "2026-04-09T19:16:00+00:00"
}