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CVE-2021-26933

Status: ModifiedMedium (5.5)—

An issue was discovered in Xen 4.9 through 4.14.x. On Arm, a guest is allowed to control whether memory accesses are bypassing the cache. This means that Xen needs to ensure that all writes (such as the ones during scrubbing) have reached the memory before handing over the page to a guest. Unfortunately, the operation to clean the cache is happening before checking if the page was scrubbed. Therefore there is no guarantee when all the writes will reach the memory.

CVSS

Exploitation probability (EPSS)

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

Affected technologies (3)

Debian — Debian LinuxFedoraproject — FedoraXEN — XEN

CWEs

References

Raw JSON (NVD)

Show
{
  "id": "CVE-2021-26933",
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          "accessVector": "LOCAL",
          "vectorString": "AV:L/AC:L/Au:N/C:P/I:N/A:N",
          "authentication": "NONE",
          "integrityImpact": "NONE",
          "accessComplexity": "LOW",
          "availabilityImpact": "NONE",
          "confidentialityImpact": "PARTIAL"
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        "acInsufInfo": false,
        "impactScore": 2.9,
        "baseSeverity": "LOW",
        "obtainAllPrivilege": false,
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          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
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  "affected": [
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  "published": "2021-02-17T02:15:13.097",
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  "vulnStatus": "Modified",
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      "lang": "en",
      "value": "An issue was discovered in Xen 4.9 through 4.14.x. On Arm, a guest is allowed to control whether memory accesses are bypassing the cache. This means that Xen needs to ensure that all writes (such as the ones during scrubbing) have reached the memory before handing over the page to a guest. Unfortunately, the operation to clean the cache is happening before checking if the page was scrubbed. Therefore there is no guarantee when all the writes will reach the memory."
    },
    {
      "lang": "es",
      "value": "Se detectó un problema en Xen versiones 4.9 hasta 4.14.x. En Arm, un invitado puede controlar si los accesos a la memoria pasan por encima de la caché. Esto significa que Xen necesita asegurarse de que todas las escrituras (como las que se producen durante el scrubbing) han llegado a la memoria antes de entregar la página a un invitado. Desgraciadamente, la operación de limpieza de la caché se realiza antes de comprobar si la página ha sido limpiada. Por lo tanto, no existe garantía de que todas las escrituras lleguen a la memoria"
    }
  ],
  "lastModified": "2026-06-17T03:44:02.227",
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