CVE-2026-63954 (GCVE-0-2026-63954)

Vulnerability from cvelistv5 – Published: 2026-07-19 14:55 – Updated: 2026-08-05 12:37
VLAI
Title
hpfs: fix a crash if hpfs_map_dnode_bitmap fails
Summary
In the Linux kernel, the following vulnerability has been resolved: hpfs: fix a crash if hpfs_map_dnode_bitmap fails If hpfs_map_dnode_bitmap fails, the code would call hpfs_brelse4 on uninitialized quad buffer head, causing a crash.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 010b08084000ef018f1a8de5197087f3b91d8cfe (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < d98d8562b3284b5a5c8eb67e71b794508e46e288 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 1648a3c7f4e18f46a4881920133fc4f2494185a0 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 7c58c55a2a16f7274772507bd1637be609351b4f (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 1d73a533760bc5abb83b3cc759133596f7bb708f (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 0886c6f257fe3663f80218aa1919b0f3f21bf22c (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 4f37bb30b57d6d403d02673074555bd3c3602bef (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 974820a59efde7c1a7e1260bcfe9bb81f833cc9f (git)
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Linux Linux Affected: 2.6.12
Unaffected: 0 , < 2.6.12 (semver)
Unaffected: 5.10.259 , ≤ 5.10.* (semver)
Unaffected: 5.15.210 , ≤ 5.15.* (semver)
Unaffected: 6.1.176 , ≤ 6.1.* (semver)
Unaffected: 6.6.143 , ≤ 6.6.* (semver)
Unaffected: 6.12.93 , ≤ 6.12.* (semver)
Unaffected: 6.18.35 , ≤ 6.18.* (semver)
Unaffected: 7.0.12 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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{
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nhpfs: fix a crash if hpfs_map_dnode_bitmap fails\n\nIf hpfs_map_dnode_bitmap fails, the code would call hpfs_brelse4 on\nuninitialized quad buffer head, causing a crash."
        }
      ],
      "metrics": [
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            "baseSeverity": "HIGH",
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            "version": "3.1"
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              "value": "AV:L - The bug is reached only through local VFS syscalls (mkdir, create, unlink, rename) on a mounted HPFS filesystem; HPFS is a local block-device filesystem with no network-facing kernel server component.\nAC:L - An attacker can reliably force `hpfs_map_dnode_bitmap()` to fail by mounting a crafted image (e.g. with `check=none` and an invalid `dir_band_bitmap`) or by corrupting the loop/backing device after mount to induce read errors, then triggering a directory operation.\nPR:L - Exploitation requires mounting HPFS (achievable with CAP_SYS_ADMIN inside an unprivileged user namespace) and write access to the mountpoint; it does not require real root in the initial namespace.\nUI:N - In the highest-impact path, the attacker mounts their own malicious HPFS image inside a user namespace and triggers the bug themselves without requiring any victim action such as plugging in media or mounting untrusted storage.\nS:U - Impact is confined to kernel memory management within the same kernel security domain; there is no crossing of VM, container, or IOMMU boundaries.\nC:H - Calling `hpfs_brelse4()` on an uninitialized `quad_buffer_head` performs `kfree()` and `brelse()` on stack garbage, which is uncontrolled memory corruption that can corrupt slab metadata or dereference arbitrary pointers, not a bounded NULL dereference.\nI:H - The erroneous `kfree()`/`brelse()` calls on uninitialized pointers can corrupt kernel heap state and potentially be leveraged for arbitrary writes, matching the guidance to score uncertain memory-corruption bugs at High.\nA:H - The bug reliably causes a kernel oops or panic when `hpfs_map_dnode_bitmap()` fails, resulting in complete loss of system availability for the affected host."
            }
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      "providerMetadata": {
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        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        {
          "url": "https://git.kernel.org/stable/c/974820a59efde7c1a7e1260bcfe9bb81f833cc9f"
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    "dateReserved": "2026-07-19T07:54:57.023Z",
    "dateUpdated": "2026-08-05T12:37:38.482Z",
    "state": "PUBLISHED"
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      "date": "2026-09-21",
      "epss": "0.00169",
      "percentile": "0.06595"
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      "product_status:known_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "hpfs: fix a crash if hpfs_map_dnode_bitmap fails",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-63954.json",
      "version": "1"
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nhpfs: fix a crash if hpfs_map_dnode_bitmap fails\n\nIf hpfs_map_dnode_bitmap fails, the code would call hpfs_brelse4 on\nuninitialized quad buffer head, causing a crash."
          }
        ],
        "id": "CVE-2026-63954",
        "lastModified": "2026-07-27T17:44:23.777",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
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              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-07-19T16:17:14.183",
        "references": [
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            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/010b08084000ef018f1a8de5197087f3b91d8cfe"
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          },
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          },
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            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/974820a59efde7c1a7e1260bcfe9bb81f833cc9f"
          },
          {
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            "url": "https://git.kernel.org/stable/c/d98d8562b3284b5a5c8eb67e71b794508e46e288"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Awaiting Analysis"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "None",
      "current_release_date": "2026-07-21T22:32:13+00:00",
      "cve": "CVE-2026-63954",
      "id": "CVE-2026-63954",
      "initial_release_date": "2026-07-19T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: hpfs: fix a crash if hpfs_map_dnode_bitmap fails",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63954.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-07-24T16:21:12Z",
      "cve": "CVE-2026-63954",
      "id": "CVE-2026-63954",
      "initial_release_date": "2026-07-21T13:02:50Z",
      "product_status:known_affected": "298",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-63954",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-63954.json",
      "version": "3"
    }
  }
}



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Tags
Taxonomy of the tags.





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

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.


Detection rules are retrieved from Rulezet.


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.