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                "id": "CVE-2024-36943",
                "options": [
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                  },
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                "timestamp": "2024-06-05T18:15:10.001170Z",
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          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
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          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
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            "url": "https://git.kernel.org/stable/c/74b3d66f91d9f539f99faad74d796fa9a389a015"
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            "url": "https://git.kernel.org/stable/c/c70dce4982ce1718bf978a35f8e26160b82081f4"
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        ],
        "title": "CVE Program Container"
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    "cna": {
      "affected": [
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          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/proc/task_mmu.c"
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "affected",
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              "versionType": "git"
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          "product": "Linux",
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "unaffected",
              "version": "0",
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              "version": "6.8.10",
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              "status": "unaffected",
              "version": "6.9",
              "versionType": "original_commit_for_fix"
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                  "vulnerable": true
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfs/proc/task_mmu: fix loss of young/dirty bits during pagemap scan\n\nmake_uffd_wp_pte() was previously doing:\n\n  pte = ptep_get(ptep);\n  ptep_modify_prot_start(ptep);\n  pte = pte_mkuffd_wp(pte);\n  ptep_modify_prot_commit(ptep, pte);\n\nBut if another thread accessed or dirtied the pte between the first 2\ncalls, this could lead to loss of that information.  Since\nptep_modify_prot_start() gets and clears atomically, the following is the\ncorrect pattern and prevents any possible race.  Any access after the\nfirst call would see an invalid pte and cause a fault:\n\n  pte = ptep_modify_prot_start(ptep);\n  pte = pte_mkuffd_wp(pte);\n  ptep_modify_prot_commit(ptep, pte);"
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H",
            "version": "3.1"
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              "lang": "en",
              "value": "AV:L - The vulnerability is reached only through the PAGEMAP_SCAN ioctl on /proc/\u003cpid\u003e/pagemap combined with a userfaultfd WP-async registration, both of which require local execution on the host. There is no network-facing consumer of this path.\nAC:L - The attacker owns both sides of the race \u2014 sibling threads continuously writing to the mapped range set the hardware A/D bits while another thread loops PAGEMAP_SCAN with PM_SCAN_WP_MATCHING over millions of PTEs per iteration, so a hit is effectively guaranteed and can be retried without limit. No condition depends on external state the attacker cannot influence.\nPR:L - Only an ordinary unprivileged local account is needed: pagemap_open() requires just PTRACE_MODE_READ (trivial for /proc/self), the PAGEMAP_SCAN ioctl has no capability check, and userfaultfd_syscall_allowed() unconditionally permits UFFD_USER_MODE_ONLY so even vm.unprivileged_userfaultfd=0 does not block UFFD_FEATURE_WP_ASYNC registration. All required Kconfig options (PROC_PAGE_MONITOR, PTE_MARKER_UFFD_WP) are default-y in distro kernels.\nUI:N - The attacker drives the ioctl and the racing writes entirely from its own threads with no victim action required; when targeting another mm the victim\u0027s pre-existing uffd-wp-async registration is passive state, not an interaction.\nS:U - The lost PTE bits corrupt memory managed by the same kernel that contains the flaw, with no crossing of a hypervisor, IOMMU, or sandbox boundary. This is the standard unchanged-scope case for a kernel memory-management defect.\nC:L - Discarding the dirty bit causes a page\u0027s rewritten contents to be dropped and the stale swap-slot contents to be resurrected, so data a process deliberately overwrote or scrubbed (keys, credentials) persists in memory and on the swap device instead of being erased. This is a bounded exposure of previously-written data rather than an arbitrary kernel read primitive.\nI:H - Loss of the dirty bit makes the kernel silently drop modified pages \u2014 swap-cached anonymous pages revert to stale contents and MADV_FREE pages are discarded to zeros via the try_to_unmap_one discard path \u2014 with no error to the application. The attacker can repeat this across an unbounded number of pages, including in another process\u0027s mm it can ptrace-read (e.g. a CRIU- or VMM-managed workload using uffd-wp-async dirty tracking), amounting to total loss of integrity of that memory.\nA:H - Pages silently reverting to stale swap contents or being zeroed out corrupts live program state and reliably renders the affected process \u2014 including a targeted uffd-wp-async user such as a checkpoint/restore agent or live-migration VMM and its guest \u2014 non-functional or crashed. The condition is repeatable at will by an unprivileged local user."
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          "url": "https://git.kernel.org/stable/c/c70dce4982ce1718bf978a35f8e26160b82081f4"
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      "title": "fs/proc/task_mmu: fix loss of young/dirty bits during pagemap scan",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2024-36943",
    "datePublished": "2024-05-30T15:35:42.119Z",
    "dateReserved": "2024-05-30T15:25:07.073Z",
    "dateUpdated": "2026-08-05T11:32:11.488Z",
    "state": "PUBLISHED"
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