CVE-2026-35195

Full vulnerability record from the local CVENow database.

Description

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.

Severity

MEDIUM

CVSS score

6.1 (v4.0)

Vulnerability status

Analyzed

Source identifier

[email protected]

Published

2026-04-09 19:16:25.500000

Last modified

2026-10-26 22:10:00.163000

View original CVE JSON

{
  "id": "CVE-2026-35195",
  "sourceIdentifier": "[email protected]",
  "published": "2026-04-09T19:16:25.500",
  "lastModified": "2026-10-26T22:10:00.163",
  "vulnStatus": "Analyzed",
  "cveTags": [],
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      "lang": "en",
      "value": "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."
    },
    {
      "lang": "es",
      "value": "Wasmtime es un entorno de ejecución para WebAssembly. Antes de las versiones 24.0.7, 36.0.7, 42.0.2 y 43.0.1, la implementación de Wasmtime para la transcodificación de cadenas entre componentes contiene un error donde el valor de retorno de un realloc de un componente invitado no se valida antes de que el anfitrión intente escribir a través del puntero. Esto permite a un invitado hacer que el anfitrión escriba bytes de cadena transcodificados arbitrarios en una ubicación arbitraria hasta 4 GiB de distancia de la base de la memoria lineal. Estas escrituras en el anfitrión podrían acceder a memoria no mapeada o podrían corromper estructuras de datos del anfitrión, dependiendo de la configuración de Wasmtime. Wasmtime, por defecto, reserva 4 GiB de memoria virtual para la memoria lineal de un invitado, lo que significa que este error, por defecto en los anfitriones, hará que el anfitrión acceda a memoria no mapeada y aborte el proceso debido a un fallo no manejado. Sin embargo, Wasmtime puede configurarse para reservar menos memoria para un invitado y para eliminar todas las páginas de protección, por lo que algunas configuraciones de Wasmtime pueden llevar a la corrupción de datos fuera de la memoria lineal de un invitado, como estructuras de datos del anfitrión o memorias lineales de otros invitados. Esta vulnerabilidad está corregida en las versiones 24.0.7, 36.0.7, 42.0.2 y 43.0.1."
    }
  ],
  "affected": [
    {
      "source": "[email protected]",
      "affectedData": [
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          "vendor": "bytecodealliance",
          "product": "wasmtime",
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              "status": "affected"
            },
            {
              "version": ">= 25.0.0, < 36.0.7",
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            },
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              "version": ">= 37.0.0, < 42.0.2",
              "status": "affected"
            },
            {
              "version": ">= 43.0.0, < 44.0.1",
              "status": "affected"
            }
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        }
      ]
    }
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    "cvssMetricV31": [
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          "id": "CVE-2026-35195",
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  "weaknesses": [
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  "references": [
    {
      "url": "https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-394w-hwhg-8vgm",
      "source": "[email protected]",
      "tags": [
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}