buffer overruns in libfsimage iso9660 handling

{
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "cveMetadata": {
    "cveId": "CVE-2026-42495",
    "assignerOrgId": "23aa2041-22e1-471f-9209-9b7396fa234f",
    "assignerShortName": "XEN",
    "dateUpdated": "2026-07-28T12:31:41.743Z",
    "dateReserved": "2026-04-27T14:20:24.139Z",
    "datePublished": "2026-07-28T12:31:41.743Z",
    "state": "PUBLISHED"
  },
  "containers": {
    "cna": {
      "providerMetadata": {
        "orgId": "23aa2041-22e1-471f-9209-9b7396fa234f",
        "shortName": "XEN",
        "dateUpdated": "2026-07-28T12:31:41.743Z"
      },
      "datePublic": "2026-07-28T12:00:00.000Z",
      "title": "buffer overruns in libfsimage iso9660 handling",
      "descriptions": [
        {
          "lang": "en",
          "value": "[This CNA information record relates to multiple CVEs; the\ntext explains which aspects/vulnerabilities correspond to which CVE.]\n\nThe directory and Rock Ridge / SUSP walk in libfsimage's iso9660 driver\nderives several lengths directly from attacker-controlled on-disk fields\nwithout validating them:\n\n * The directory loop itself assumes a good record length.  This is\n   CVE-2026-42494.\n\n * The calculation of the System Use area may underflow.  This is\n   CVE-2026-42495.\n\n * The Rock Ridge extension loop assumes a good (inner) record length.\n   This is CVE-2026-62423.\n\n * The Rock Ridge NM record processing assumes a good entry length.\n   This is CVE-2026-62424.\n\n * The Rock Ridge CE record processing assumes a good size and offset.\n   This is CVE-2026-62425."
        }
      ],
      "affected": [
        {
          "vendor": "Xen",
          "product": "Xen",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "consult Xen advisory XSA-497",
              "status": "unknown"
            }
          ]
        }
      ],
      "references": [
        {
          "url": "https://xenbits.xenproject.org/xsa/advisory-497.html"
        }
      ],
      "impacts": [
        {
          "descriptions": [
            {
              "lang": "en",
              "value": "A guest using pygrub can escalate its privilege to that of the domain\nconstruction tools (i.e., normally, to control of the host).\n\nIf the mechanism introduced by XSA-443 (see the mitigation section below)\nis in use, then the guest can only escalate to this limited context."
            }
          ]
        }
      ],
      "configurations": [
        {
          "lang": "en",
          "value": "All Xen versions from at least 3.2 onwards are affected.  Older versions\nhave not been inspected."
        }
      ],
      "workarounds": [
        {
          "lang": "en",
          "value": "XSA-443 added a mechanism to run pygrub de-privileged.  Using this mode\nwill mitigate the vulnerability.\n\nEnsuring that guests do not use the pygrub bootloader will avoid this\nvulnerability.\n\nFor cases where the PV guest is known to be 64bit, and uses grub2 as a\nbootloader, pvgrub is a suitable alternative to pygrub.\n\nRunning only HVM or PVH guests will avoid the vulnerability."
        }
      ],
      "credits": [
        {
          "lang": "en",
          "value": "This issue was discovered by Syed Abdul Khaliq of BugQore.",
          "type": "finder"
        }
      ]
    }
  }
}