High

rust-wasmtime — security advisory

Type: advisorySources: OSVAdvisory ID: UBUNTU-CVE-2026-34941

Wasmtime is a runtime for WebAssembly. Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, Wasmtime contains a vulnerability where when transcoding a UTF-16 string to the latin1+utf16 component-model encoding it would incorrectly validate the byte length of the input string when performing a bounds check. Specifically the number of code units were checked instead of the byte length, which is twice the size of the code units. This vulnerability can cause the host to read beyond the end of a WebAssembly's linear memory in an attempt to transcode nonexistent bytes. In Wasmtime's default configuration this will read unmapped memory on a guard page, terminating the process with a segfault. Wasmtime can be configured, however, without guard pages which would mean that host memory beyond the end of linear memory may be read and interpreted as UTF-16. A host segfault is a denial-of-service vulnerability in Wasmtime, and possibly being able to read beyond the end of linear memory is additionally a vulnerability. Note that reading beyond the end of linear memory requires nonstandard configuration of Wasmtime, specifically with guard pages disabled. 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-2026-34941
Confirmed fixed CVEs: Not specified
Updated in this feed: 31 Oct 2026, 03:02 UTC · Revision 1

Source evidence

UBUNTU-CVE-2026-34941

core-osv · Original source

Published 9 Apr 2026, 19:16 UTC

osv:UBUNTU-CVE-2026-34941

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": "2a618c0c7b31debccfc3893d102cf5969cd7f0b99e449fdea34c385cf79d966c",
  "url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-34941",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "UBUNTU-CVE-2026-34941",
    "summary": "Wasmtime is a runtime for WebAssembly. Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, Wasmtime contains a vulnerability where when transcoding a UTF-16 string to the latin1+utf16 component-model encoding it would incorrectly validate the byte length of the input string when performing a bounds check. Specifically the number of code units were checked instead of the byte length, which is twice the size of the code units. This vulnerability can cause the host to read beyond the end of a WebAssembly's linear memory in an attempt to transcode nonexistent bytes. In Wasmtime's default configuration this will read unmapped memory on a guard page, terminating the process with a segfault. Wasmtime can be configured, however, without guard pages which would mean that host memory beyond the end of linear memory may be read and interpreted as UTF-16. A host segfault is a denial-of-service vulnerability in Wasmtime, and possibly being able to read beyond the end of linear memory is additionally a vulnerability. Note that reading beyond the end of linear memory requires nonstandard configuration of Wasmtime, specifically with guard pages disabled. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1.",
    "evidence": "osv:UBUNTU-CVE-2026-34941",
    "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": "high",
    "structured": {
      "id": "UBUNTU-CVE-2026-34941",
      "aliases": [
        "UBUNTU-CVE-2026-34941"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/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:H/I:N/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-2026-34941.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-2026-34941.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-2026-34941.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-2026-34941.json"
          },
          "ecosystem_specific": {
            "binaries": [
              {
                "binary_name": "librust-cranelift-dev",
                "binary_version": "0.123.5+36.0.5+dfsg-1"
              }
            ]
          }
        }
      ],
      "modified": "2026-10-17T13:00:02.907869412Z",
      "provider": "osv",
      "upstream": [
        "CVE-2026-34941"
      ],
      "references": [
        "https://ubuntu.com/security/CVE-2026-34941",
        "https://www.cve.org/CVERecord?id=CVE-2026-34941",
        "https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-hx6p-xpx3-jvvv"
      ]
    },
    "related_cves": [
      {
        "value": "CVE-2026-34941",
        "evidence": "/upstream"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/1/score"
  },
  "source_id": "core-osv",
  "document_id": 360191,
  "published_at": "2026-04-09T19:16:00+00:00"
}