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EUVD-2026-346270

European Vulnerability Database identifier assigned by ENISA

Reserved

2026-10-02 08:08

Assigner

ENISA

Alias of

a CVE record, shown under related vulnerabilities. This identifier carries no description, severity or references of its own: they belong to that CVE.

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{
  "assigner": "ENISA",
  "date_reserved": "2026-10-02T08:08:11.216645+00:00",
  "id": "EUVD-2026-346270"
}

CVE-2024-50066 (GCVE-0-2024-50066)

Vulnerability from cvelistv5 – Published: 2024-10-23 05:20 – Updated: 2026-08-05 11:41

Title

mm/mremap: fix move_normal_pmd/retract_page_tables race

Summary

In the Linux kernel, the following vulnerability has been resolved: mm/mremap: fix move_normal_pmd/retract_page_tables race In mremap(), move_page_tables() looks at the type of the PMD entry and the specified address range to figure out by which method the next chunk of page table entries should be moved. At that point, the mmap_lock is held in write mode, but no rmap locks are held yet. For PMD entries that point to page tables and are fully covered by the source address range, move_pgt_entry(NORMAL_PMD, ...) is called, which first takes rmap locks, then does move_normal_pmd(). move_normal_pmd() takes the necessary page table locks at source and destination, then moves an entire page table from the source to the destination. The problem is: The rmap locks, which protect against concurrent page table removal by retract_page_tables() in the THP code, are only taken after the PMD entry has been read and it has been decided how to move it. So we can race as follows (with two processes that have mappings of the same tmpfs file that is stored on a tmpfs mount with huge=advise); note that process A accesses page tables through the MM while process B does it through the file rmap: process A process B ========= ========= mremap mremap_to move_vma move_page_tables get_old_pmd alloc_new_pmd *** PREEMPT *** madvise(MADV_COLLAPSE) do_madvise madvise_walk_vmas madvise_vma_behavior madvise_collapse hpage_collapse_scan_file collapse_file retract_page_tables i_mmap_lock_read(mapping) pmdp_collapse_flush i_mmap_unlock_read(mapping) move_pgt_entry(NORMAL_PMD, ...) take_rmap_locks move_normal_pmd drop_rmap_locks When this happens, move_normal_pmd() can end up creating bogus PMD entries in the line `pmd_populate(mm, new_pmd, pmd_pgtable(pmd))`. The effect depends on arch-specific and machine-specific details; on x86, you can end up with physical page 0 mapped as a page table, which is likely exploitable for user->kernel privilege escalation. Fix the race by letting process B recheck that the PMD still points to a page table after the rmap locks have been taken. Otherwise, we bail and let the caller fall back to the PTE-level copying path, which will then bail immediately at the pmd_none() check. Bug reachability: Reaching this bug requires that you can create shmem/file THP mappings - anonymous THP uses different code that doesn't zap stuff under rmap locks. File THP is gated on an experimental config flag (CONFIG_READ_ONLY_THP_FOR_FS), so on normal distro kernels you need shmem THP to hit this bug. As far as I know, getting shmem THP normally requires that you can mount your own tmpfs with the right mount flags, which would require creating your own user+mount namespace; though I don't know if some distros maybe enable shmem THP by default or something like that. Bug impact: This issue can likely be used for user->kernel privilege escalation when it is reachable.

Severity

7.8 (High)


                        
                          CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

7 (High)


                        
                          CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

SSVC

Exploitation: poc Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2024-11-23 04:55 UTC

CWE

CWE-362 - Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

Assigner

Linux mitre root Scorecard

References

6 references

URL	Tags
https://git.kernel.org/stable/c/17396e32f975130b3…
https://git.kernel.org/stable/c/1552ce9ce8af47c0f…
https://git.kernel.org/stable/c/6fa1066fc5d00cb9f…
https://project-zero.issues.chromium.org/issues/3…
https://www.vicarius.io/vsociety/posts/cve-2024-5…
https://www.vicarius.io/vsociety/posts/cve-2024-5…

Impacted products

3 products

Vendor	Product	Version
Linux	Linux	Affected: 1d65b771bc08cd054cf6d3766a72e113dc46d62f , < 17396e32f975130b3e6251f024c8807d192e4c3e (git) Affected: 1d65b771bc08cd054cf6d3766a72e113dc46d62f , < 1552ce9ce8af47c0fe911682e5e1855e25851ca9 (git) Affected: 1d65b771bc08cd054cf6d3766a72e113dc46d62f , < 6fa1066fc5d00cb9f1b0e83b7ff6ef98d26ba2aa (git)
Linux	Linux	Affected: 6.6 Unaffected: 0 , < 6.6 (semver) Unaffected: 6.6.58 , ≤ 6.6.* (semver) Unaffected: 6.11.5 , ≤ 6.11.* (semver) Unaffected: 6.12 , ≤ * (original_commit_for_fix)
linux	linux_kernel	Affected: 6.6 , < 6.6.58 (custom) Unaffected: 6.6.58 , < 6.7 (custom) Unaffected: 6.11.5 , < 6.12 (custom) Unaffected: 6.12 , < * (custom) Affected: 1d65b771bc08 , < 17396e32f975 (git) Affected: 1d65b771bc08 , < 1552ce9ce8af (git) Affected: 1d65b771bc08 , < 6fa1066fc5d0 (git) cpe:2.3:o:linux:linux_kernel::::::::

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JSON

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{
  "containers": {
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        "affected": [
          {
            "cpes": [
              "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*"
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                "version": "6.11.5",
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                "status": "unaffected",
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        ],
        "metrics": [
          {
            "cvssV3_1": {
              "attackComplexity": "HIGH",
              "attackVector": "LOCAL",
              "availabilityImpact": "HIGH",
              "baseScore": 7,
              "baseSeverity": "HIGH",
              "confidentialityImpact": "HIGH",
              "integrityImpact": "HIGH",
              "privilegesRequired": "LOW",
              "scope": "UNCHANGED",
              "userInteraction": "NONE",
              "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
              "version": "3.1"
            }
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          {
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              "content": {
                "id": "CVE-2024-50066",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2024-11-23T04:55:50.463779Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "problemTypes": [
          {
            "descriptions": [
              {
                "cweId": "CWE-362",
                "description": "CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization (\u0027Race Condition\u0027)",
                "lang": "en",
                "type": "CWE"
              }
            ]
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2024-11-25T14:12:03.999Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
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        "providerMetadata": {
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          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
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        },
        "references": [
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            "url": "https://www.vicarius.io/vsociety/posts/cve-2024-50066-kernel-mitigation-vulnerability"
          },
          {
            "url": "https://www.vicarius.io/vsociety/posts/cve-2024-50066-kernel-detection-vulnerability"
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        "title": "CVE Program Container",
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/mremap: fix move_normal_pmd/retract_page_tables race\n\nIn mremap(), move_page_tables() looks at the type of the PMD entry and the\nspecified address range to figure out by which method the next chunk of\npage table entries should be moved.\n\nAt that point, the mmap_lock is held in write mode, but no rmap locks are\nheld yet.  For PMD entries that point to page tables and are fully covered\nby the source address range, move_pgt_entry(NORMAL_PMD, ...) is called,\nwhich first takes rmap locks, then does move_normal_pmd(). \nmove_normal_pmd() takes the necessary page table locks at source and\ndestination, then moves an entire page table from the source to the\ndestination.\n\nThe problem is: The rmap locks, which protect against concurrent page\ntable removal by retract_page_tables() in the THP code, are only taken\nafter the PMD entry has been read and it has been decided how to move it. \nSo we can race as follows (with two processes that have mappings of the\nsame tmpfs file that is stored on a tmpfs mount with huge=advise); note\nthat process A accesses page tables through the MM while process B does it\nthrough the file rmap:\n\nprocess A                      process B\n=========                      =========\nmremap\n  mremap_to\n    move_vma\n      move_page_tables\n        get_old_pmd\n        alloc_new_pmd\n                      *** PREEMPT ***\n                               madvise(MADV_COLLAPSE)\n                                 do_madvise\n                                   madvise_walk_vmas\n                                     madvise_vma_behavior\n                                       madvise_collapse\n                                         hpage_collapse_scan_file\n                                           collapse_file\n                                             retract_page_tables\n                                               i_mmap_lock_read(mapping)\n                                               pmdp_collapse_flush\n                                               i_mmap_unlock_read(mapping)\n        move_pgt_entry(NORMAL_PMD, ...)\n          take_rmap_locks\n          move_normal_pmd\n          drop_rmap_locks\n\nWhen this happens, move_normal_pmd() can end up creating bogus PMD entries\nin the line `pmd_populate(mm, new_pmd, pmd_pgtable(pmd))`.  The effect\ndepends on arch-specific and machine-specific details; on x86, you can end\nup with physical page 0 mapped as a page table, which is likely\nexploitable for user-\u003ekernel privilege escalation.\n\nFix the race by letting process B recheck that the PMD still points to a\npage table after the rmap locks have been taken.  Otherwise, we bail and\nlet the caller fall back to the PTE-level copying path, which will then\nbail immediately at the pmd_none() check.\n\nBug reachability: Reaching this bug requires that you can create\nshmem/file THP mappings - anonymous THP uses different code that doesn\u0027t\nzap stuff under rmap locks.  File THP is gated on an experimental config\nflag (CONFIG_READ_ONLY_THP_FOR_FS), so on normal distro kernels you need\nshmem THP to hit this bug.  As far as I know, getting shmem THP normally\nrequires that you can mount your own tmpfs with the right mount flags,\nwhich would require creating your own user+mount namespace; though I don\u0027t\nknow if some distros maybe enable shmem THP by default or something like\nthat.\n\nBug impact: This issue can likely be used for user-\u003ekernel privilege\nescalation when it is reachable."
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              "value": "AV:L - Both halves of the race are driven by local syscalls \u2014 `mremap()` in one process and `madvise(MADV_COLLAPSE)` in another (or background khugepaged) \u2014 against a shared tmpfs mapping. No network or physical access is involved.\nAC:L - The attacker controls both sides of the race: it runs process A\u0027s `mremap()` and process B\u0027s `MADV_COLLAPSE` on the same tmpfs file, and the window sits around a documented preemption/allocation point between `alloc_new_pmd()` and `move_pgt_entry(NORMAL_PMD, ...)`, so it can be widened with CPU pinning/memory pressure and retried indefinitely. Setting up shmem THP is an attacker-performed runtime action (`mount -t tmpfs -o huge=advise` inside its own user+mount namespace), not a condition beyond its control.\nPR:L - An ordinary unprivileged local user suffices \u2014 `mremap()` and `madvise(MADV_COLLAPSE)` have no capability checks, and the tmpfs `huge=` option is explicitly ungated (only `noswap`/`quota` require init_user_ns + CAP_SYS_ADMIN), so the required shmem THP mount is obtainable via unprivileged user+mount namespaces, which are enabled by default on major distros.\nUI:N - The attacker spawns and drives both racing processes itself; no victim action, mount, or file access by another user is required.\nS:U - This is a standard local kernel privilege escalation \u2014 the corruption occurs in kernel page tables and the impact stays within the same security authority (the OS kernel), with no VM/IOMMU boundary crossed.\nC:H - Physical page 0 gets installed as a live user-accessible page table, so its arbitrary contents are interpreted as PTEs, mapping attacker-reachable physical memory into userspace and enabling disclosure of kernel memory and other processes\u0027 data.\nI:H - The bogus page table yields an arbitrary physical memory write primitive (PTEs derived from page 0 carry `_PAGE_RW|_PAGE_USER`), allowing overwrite of kernel data such as `cred` structures; the reporter states it is likely exploitable for user-\u003ekernel privilege escalation.\nA:H - Corrupting the page-table tree with PFN 0, hitting `VM_BUG_ON`, and later freeing physical page 0 into the buddy allocator reliably produces kernel oops/panic and system-wide memory corruption."
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Sightings

Author	Source	Type	Date	Other

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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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EUVD-2026-346270

CVE-2024-50066 (GCVE-0-2024-50066)

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Nomenclature

Related by attack behaviour