CVE-2024-50102 (GCVE-0-2024-50102)

Vulnerability from cvelistv5 – Published: 2024-11-05 17:10 – Updated: 2026-05-11 20:45
VLAI
Title
x86: fix user address masking non-canonical speculation issue
Summary
In the Linux kernel, the following vulnerability has been resolved: x86: fix user address masking non-canonical speculation issue It turns out that AMD has a "Meltdown Lite(tm)" issue with non-canonical accesses in kernel space. And so using just the high bit to decide whether an access is in user space or kernel space ends up with the good old "leak speculative data" if you have the right gadget using the result: CVE-2020-12965 “Transient Execution of Non-Canonical Accesses“ Now, the kernel surrounds the access with a STAC/CLAC pair, and those instructions end up serializing execution on older Zen architectures, which closes the speculation window. But that was true only up until Zen 5, which renames the AC bit [1]. That improves performance of STAC/CLAC a lot, but also means that the speculation window is now open. Note that this affects not just the new address masking, but also the regular valid_user_address() check used by access_ok(), and the asm version of the sign bit check in the get_user() helpers. It does not affect put_user() or clear_user() variants, since there's no speculative result to be used in a gadget for those operations.
Severity
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2025-10-01 20:22 UTC
CWE
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: b19b74bc99b1501a550f4448d04d59b946dc617a , < 291313693677a345d4f50aae3c68e28b469f601e (git)
Affected: b19b74bc99b1501a550f4448d04d59b946dc617a , < 86e6b1547b3d013bc392adf775b89318441403c2 (git)
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Linux Linux Affected: 6.4
Unaffected: 0 , < 6.4 (semver)
Unaffected: 6.11.6 , ≤ 6.11.* (semver)
Unaffected: 6.12 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Show details on NVD website
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              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
                {
                  "status": "affected",
                  "version": "6.4"
                },
                {
                  "lessThan": "6.4",
                  "status": "unaffected",
                  "version": "0",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.11.*",
                  "status": "unaffected",
                  "version": "6.11.6",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "*",
                  "status": "unaffected",
                  "version": "6.12",
                  "versionType": "original_commit_for_fix"
                }
              ]
            }
          ],
          "cpeApplicability": [
            {
              "nodes": [
                {
                  "cpeMatch": [
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.11.6",
                      "versionStartIncluding": "6.4",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.12",
                      "versionStartIncluding": "6.4",
                      "vulnerable": true
                    }
                  ],
                  "negate": false,
                  "operator": "OR"
                }
              ]
            }
          ],
          "descriptions": [
            {
              "lang": "en",
              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nx86: fix user address masking non-canonical speculation issue\n\nIt turns out that AMD has a \"Meltdown Lite(tm)\" issue with non-canonical\naccesses in kernel space.  And so using just the high bit to decide\nwhether an access is in user space or kernel space ends up with the good\nold \"leak speculative data\" if you have the right gadget using the\nresult:\n\n  CVE-2020-12965 \u201cTransient Execution of Non-Canonical Accesses\u201c\n\nNow, the kernel surrounds the access with a STAC/CLAC pair, and those\ninstructions end up serializing execution on older Zen architectures,\nwhich closes the speculation window.\n\nBut that was true only up until Zen 5, which renames the AC bit [1].\nThat improves performance of STAC/CLAC a lot, but also means that the\nspeculation window is now open.\n\nNote that this affects not just the new address masking, but also the\nregular valid_user_address() check used by access_ok(), and the asm\nversion of the sign bit check in the get_user() helpers.\n\nIt does not affect put_user() or clear_user() variants, since there\u0027s no\nspeculative result to be used in a gadget for those operations."
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2025-05-04T09:46:02.268Z",
            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "shortName": "Linux"
          },
          "references": [
            {
              "url": "https://git.kernel.org/stable/c/291313693677a345d4f50aae3c68e28b469f601e"
            },
            {
              "url": "https://git.kernel.org/stable/c/86e6b1547b3d013bc392adf775b89318441403c2"
            }
          ],
          "title": "x86: fix user address masking non-canonical speculation issue",
          "x_generator": {
            "engine": "bippy-1.2.0"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "assignerShortName": "Linux",
        "cveId": "CVE-2024-50102",
        "datePublished": "2024-11-05T17:10:37.986Z",
        "dateReserved": "2024-10-21T19:36:19.946Z",
        "dateUpdated": "2025-10-01T20:27:18.489Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.1"
    }
  }
}



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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.

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  • 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.