CVE-2026-72380

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: xen/pvcalls: bound backend response req_id before indexing rsp[] pvcalls_front_event_handler() takes req_id directly from the backend-supplied ring response and uses it to index the fixed-size bedata->rsp[] array for a memcpy() and a store, with no range check. A malicious or buggy backend can set req_id past PVCALLS_NR_RSP_PER_RING and drive an out-of-bounds write past the bedata allocation. req_id was also declared int while the wire field rsp->req_id is u32, so a range check on the signed value alone is insufficient: a backend req_id of 0xffffffff becomes -1, passes a >= PVCALLS_NR_RSP_PER_RING test and indexes bedata->rsp[-1]. Declare req_id as u32 so a single bound covers both ends. A backend that sends an out-of-range req_id has violated the wire protocol, so rather than silently dropping the response, log once and stop trusting the backend: set bedata->disabled. The event handler then ignores further responses, and the request paths that wait for a response return -EIO instead of blocking forever. This mirrors the fatal-error handling xen-netback uses (xenvif_fatal_tx_err()). The pvcalls frontend currently trusts its backend, so this is not a classic-Xen security issue, but it matters for hardening PV frontends against malicious backends (confidential and disaggregated deployments).

Severity

HIGH

CVSS score

8.8 (v3.1)

Vulnerability status

Received

Source identifier

416baaa9-dc9f-4396-8d5f-8c081fb06d67

Published

2026-08-15 06:22:11.493000

Last modified

2026-10-30 13:19:50.477000

View original CVE JSON

{
  "id": "CVE-2026-72380",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-08-15T06:22:11.493",
  "lastModified": "2026-10-30T13:19:50.477",
  "vulnStatus": "Received",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxen/pvcalls: bound backend response req_id before indexing rsp[]\n\npvcalls_front_event_handler() takes req_id directly from the\nbackend-supplied ring response and uses it to index the fixed-size\nbedata->rsp[] array for a memcpy() and a store, with no range check. A\nmalicious or buggy backend can set req_id past PVCALLS_NR_RSP_PER_RING\nand drive an out-of-bounds write past the bedata allocation.\n\nreq_id was also declared int while the wire field rsp->req_id is u32, so\na range check on the signed value alone is insufficient: a backend\nreq_id of 0xffffffff becomes -1, passes a >= PVCALLS_NR_RSP_PER_RING\ntest and indexes bedata->rsp[-1]. Declare req_id as u32 so a single\nbound covers both ends.\n\nA backend that sends an out-of-range req_id has violated the wire\nprotocol, so rather than silently dropping the response, log once and\nstop trusting the backend: set bedata->disabled. The event handler then\nignores further responses, and the request paths that wait for a\nresponse return -EIO instead of blocking forever. This mirrors the\nfatal-error handling xen-netback uses (xenvif_fatal_tx_err()).\n\nThe pvcalls frontend currently trusts its backend, so this is not a\nclassic-Xen security issue, but it matters for hardening PV frontends\nagainst malicious backends (confidential and disaggregated deployments)."
    }
  ],
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "programFiles": [
            "drivers/xen/pvcalls-front.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "2195046bfd69e487d9a76dc47840f15c8412840c",
              "lessThan": "4aaf7f32f1569e2c0475e073b8d7ec63b231d4c6",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "2195046bfd69e487d9a76dc47840f15c8412840c",
              "lessThan": "72e27ef70a20298e60a1de438f3628c515dea895",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "2195046bfd69e487d9a76dc47840f15c8412840c",
              "lessThan": "ede7a60b046d8b7288651c55198574ed7c259da7",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "2195046bfd69e487d9a76dc47840f15c8412840c",
              "lessThan": "bc8f2d1c6f7cf6e6551c00eb582baf4b52a04794",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "2195046bfd69e487d9a76dc47840f15c8412840c",
              "lessThan": "d1297a9e2fd6ce08678b370d41bc980ca798f809",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "2195046bfd69e487d9a76dc47840f15c8412840c",
              "lessThan": "d33846c8dcc06b83b7acdeac1e8bfbb5c0c26cb2",
              "versionType": "git",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "programFiles": [
            "drivers/xen/pvcalls-front.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "4.15",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "4.15",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.1.191",
              "lessThanOrEqual": "6.1.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.6.160",
              "lessThanOrEqual": "6.6.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.12.114",
              "lessThanOrEqual": "6.12.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.18.57",
              "lessThanOrEqual": "6.18.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.1.5",
              "lessThanOrEqual": "7.1.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.2",
              "lessThanOrEqual": "*",
              "versionType": "original_commit_for_fix",
              "status": "unaffected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "baseScore": 8.8,
          "baseSeverity": "HIGH",
          "attackVector": "ADJACENT_NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 5.9
      }
    ]
  },
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/4aaf7f32f1569e2c0475e073b8d7ec63b231d4c6",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/72e27ef70a20298e60a1de438f3628c515dea895",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/bc8f2d1c6f7cf6e6551c00eb582baf4b52a04794",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/d1297a9e2fd6ce08678b370d41bc980ca798f809",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/d33846c8dcc06b83b7acdeac1e8bfbb5c0c26cb2",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/ede7a60b046d8b7288651c55198574ed7c259da7",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ]
}