CVE-2026-80724 (GCVE-0-2026-80724)

Vulnerability from cvelistv5 – Published: 2026-08-28 07:03 – Updated: 2026-09-07 15:45
VLAI
Title
ptp: vmclock: prevent read-only mappings from becoming writable
Summary
In the Linux kernel, the following vulnerability has been resolved: ptp: vmclock: prevent read-only mappings from becoming writable vmclock_miscdev_mmap() rejects writable mappings of the shared vmclock ABI page with -EROFS, but leaves VM_MAYWRITE set. Userspace can map the page read-only and then upgrade it to writable with mprotect(), after which the guest can corrupt the host-written timekeeping data (sequence counter, UTC time, TSC offset) that the vmclock ABI defines as read-only. Clear VM_MAYWRITE on the read-only path so the mapping cannot be upgraded, as i915 does for its read-only objects and as fixed in drm/vc4 (CVE-2026-68445) and drm/panthor (CVE-2024-53071).
Severity
8.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 20503272422693d793b84f88bf23fe4e955d3a33 , < 5b4f2bec7bea6c04084d720d731bedee7caf878d (git)
Affected: 20503272422693d793b84f88bf23fe4e955d3a33 , < 3f5677d2f817355147337f0453174c7bb0f3b66a (git)
Affected: 20503272422693d793b84f88bf23fe4e955d3a33 , < 2496e141827102d6af512950057d402a2cfb2bfc (git)
Affected: 20503272422693d793b84f88bf23fe4e955d3a33 , < 2e596e7814ba38cdc129991058b6c254ed37cb11 (git)
Affected: 20503272422693d793b84f88bf23fe4e955d3a33 , < 0ce59c4148ecd1520c5592a63bb3c8991ee2d326 (git)
Affected: 20503272422693d793b84f88bf23fe4e955d3a33 , < a5edadbae57e2298a56cf7a4e774a027905a331f (git)
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Linux Linux Affected: 6.13
Unaffected: 0 , < 6.13 (semver)
Unaffected: 6.18.47 , ≤ 6.18.* (semver)
Unaffected: 6.18.50 , ≤ 6.18.* (semver)
Unaffected: 7.1.11 , ≤ 7.1.* (semver)
Unaffected: 7.2.1 , ≤ 7.2.* (semver)
Unaffected: 7.2.4 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)
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        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nptp: vmclock: prevent read-only mappings from becoming writable\n\nvmclock_miscdev_mmap() rejects writable mappings of the shared vmclock\nABI page with -EROFS, but leaves VM_MAYWRITE set.  Userspace can map the\npage read-only and then upgrade it to writable with mprotect(), after\nwhich the guest can corrupt the host-written timekeeping data (sequence\ncounter, UTC time, TSC offset) that the vmclock ABI defines as read-only.\n\nClear VM_MAYWRITE on the read-only path so the mapping cannot be\nupgraded, as i915 does for its read-only objects and as fixed in drm/vc4\n(CVE-2026-68445) and drm/panthor (CVE-2024-53071)."
        }
      ],
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        {
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Exploitation requires local syscalls to open /dev/vmclock0, mmap the shared ABI page read-only, mprotect it writable, and write host-authoritative fields; there is no network, Bluetooth, or physical-device path to vmclock_miscdev_mmap().\nAC:L - Any process that can open the misc device can reliably mmap(PROT_READ), mprotect(PROT_WRITE), and corrupt the page without races, special memory layout, or timing; VM_MAYWRITE left set is the sole missing check and mprotect honors it per mm/mprotect.c.\nPR:L - vmclock_miscdev_open() performs no capability checks; AWS ClockBound documents chmod a+r on /dev/vmclock0 for unprivileged latency-sensitive apps on EC2/Amazon Linux, so a normal tenant user on affected cloud VMs can reach the bug without root or user-namespace admin caps.\nUI:N - The attacker process performs the full open/mmap/mprotect/write sequence itself; no victim mount, click, or other user action is required beyond the attacker already having local shell access.\nS:C - The vmclock ABI page is hypervisor-written shared memory whose seq_count, UTC time, and TSC offset must stay guest-read-only; mprotect bypass lets a guest user corrupt that host-authoritative data, crossing the guest/hypervisor trust boundary rather than staying within guest-kernel scope alone.\nC:H - Unauthorized writes let an attacker race seq_count updates and corrupt in-flight host-populated fields, yielding torn reads of timekeeping data to other guest consumers and potentially exposing transient host-written values that read-only mmap alone would not reliably observe.\nI:H - After mprotect, the attacker gains arbitrary modification of host-written vmclock_abi fields (seq_count, disruption_marker, counter_value, time_sec, flags), breaking integrity of authoritative timekeeping and migration/disruption signaling relied on by guest kernel PTP and userspace ClockBound consumers.\nA:H - Corrupting seq_count, clock_status, or disruption/vm_generation markers can force ETIMEDOUT/-EINVAL in vmclock_get_crosststamp, trigger false migration/disruption handling, and cause latency-sensitive services to withdraw or fail, producing severe availability loss on affected cloud VMs."
            }
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    "datePublished": "2026-08-28T07:03:08.410Z",
    "dateReserved": "2026-08-26T14:34:25.788Z",
    "dateUpdated": "2026-09-07T15:45:07.221Z",
    "state": "PUBLISHED"
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nptp: vmclock: prevent read-only mappings from becoming writable\n\nvmclock_miscdev_mmap() rejects writable mappings of the shared vmclock\nABI page with -EROFS, but leaves VM_MAYWRITE set.  Userspace can map the\npage read-only and then upgrade it to writable with mprotect(), after\nwhich the guest can corrupt the host-written timekeeping data (sequence\ncounter, UTC time, TSC offset) that the vmclock ABI defines as read-only.\n\nClear VM_MAYWRITE on the read-only path so the mapping cannot be\nupgraded, as i915 does for its read-only objects and as fixed in drm/vc4\n(CVE-2026-68445) and drm/panthor (CVE-2024-53071)."
          }
        ],
        "id": "CVE-2026-80724",
        "lastModified": "2026-09-07T16:17:29.930",
        "metrics": {
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                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 8.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "CHANGED",
                "userInteraction": "NONE",
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    "redhat_vex": {
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      "current_release_date": "2026-08-31T15:07:43+00:00",
      "cve": "CVE-2026-80724",
      "id": "CVE-2026-80724",
      "initial_release_date": "2026-08-28T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: ptp: vmclock: prevent read-only mappings from becoming writable",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-80724.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-08T00:08:53Z",
      "cve": "CVE-2026-80724",
      "id": "CVE-2026-80724",
      "initial_release_date": "2026-08-28T16:33:00Z",
      "product_status:known_not_affected": "353",
      "product_status:recommended": "4",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-80724",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-80724.json",
      "version": "5"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.