Vulnerability-Lookup

FKIE_CVE-2026-63802

Vulnerability from fkie_nvd - Published: 2026-07-19 12:16 - Updated: 2026-08-17 05:17

Severity

7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Summary

In the Linux kernel, the following vulnerability has been resolved: blk-cgroup: fix UAF in __blkcg_rstat_flush() When multiple blkgs in the same blkcg are released concurrently, a use-after-free can occur. The race happens when one blkg's __blkcg_rstat_flush() removes another blkg's iostat entries via llist_del_all(). The second blkg sees an empty list and proceeds to free itself while the first is still iterating over its entries. Move the flush from __blkg_release() (RCU callback) to blkg_release() (before call_rcu). This ensures the RCU grace period waits for any concurrent flush's rcu_read_lock() section to complete before freeing.

References

URL	Tags
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/0ab5ee5a1badb58cbb2242617cb01a4972b1f2a2	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/5e5b7f2ef854936e95dceb6a2fdfefcb7152d2c6	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/96e545410c4f74c89d496c1d5d9ef8d08f14368b	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/afebe44facc48a61761e885bbb7f0380d4a603ec	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/bbebd9425cad3573d1527441753899b926525a0f	Patch

Impacted products

Vendor	Product	Version
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	6.4
linux	linux_kernel	6.4

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "block/blk-cgroup.c"
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              "status": "unaffected",
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            },
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              "version": "7.1.3",
              "versionType": "semver"
            },
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              "status": "unaffected",
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        }
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    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nblk-cgroup: fix UAF in __blkcg_rstat_flush()\n\nWhen multiple blkgs in the same blkcg are released concurrently,\na use-after-free can occur. The race happens when one blkg\u0027s\n__blkcg_rstat_flush() removes another blkg\u0027s iostat entries via\nllist_del_all(). The second blkg sees an empty list and proceeds\nto free itself while the first is still iterating over its entries.\n\nMove the flush from __blkg_release() (RCU callback) to blkg_release()\n(before call_rcu). This ensures the RCU grace period waits for any\nconcurrent flush\u0027s rcu_read_lock() section to complete before freeing."
    }
  ],
  "id": "CVE-2026-63802",
  "lastModified": "2026-08-17T05:17:16.727",
  "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"
      }
    ]
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
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      "url": "https://git.kernel.org/stable/c/0ab5ee5a1badb58cbb2242617cb01a4972b1f2a2"
    },
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
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    },
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    },
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    },
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  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-416"
        }
      ],
      "source": "nvd@nist.gov",
      "type": "Primary"
    }
  ]
}

CVE-2026-63802 (GCVE-0-2026-63802)

Vulnerability from cvelistv5 – Published: 2026-07-19 12:02 – Updated: 2026-08-17 04:51

Title

blk-cgroup: fix UAF in __blkcg_rstat_flush()

Summary

Severity

7.8 (High)


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

Assigner

Linux mitre root

References

5 references

URL	Tags
https://git.kernel.org/stable/c/96e545410c4f74c89…
https://git.kernel.org/stable/c/bbebd9425cad3573d…
https://git.kernel.org/stable/c/5e5b7f2ef854936e9…
https://git.kernel.org/stable/c/afebe44facc48a617…
https://git.kernel.org/stable/c/0ab5ee5a1badb58cb…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 20cb1c2fb7568a6054c55defe044311397e01ddb , < 96e545410c4f74c89d496c1d5d9ef8d08f14368b (git) Affected: 20cb1c2fb7568a6054c55defe044311397e01ddb , < bbebd9425cad3573d1527441753899b926525a0f (git) Affected: 20cb1c2fb7568a6054c55defe044311397e01ddb , < 5e5b7f2ef854936e95dceb6a2fdfefcb7152d2c6 (git) Affected: 20cb1c2fb7568a6054c55defe044311397e01ddb , < afebe44facc48a61761e885bbb7f0380d4a603ec (git) Affected: 20cb1c2fb7568a6054c55defe044311397e01ddb , < 0ab5ee5a1badb58cbb2242617cb01a4972b1f2a2 (git) Affected: 0f6090d90f627d8c58f939067d6c6821ce1b3c68 (git) Affected: 6.3.9 , < 6.4 (semver)
Linux	Linux	Affected: 6.4 Unaffected: 0 , < 6.4 (semver) Unaffected: 6.6.144 , ≤ 6.6.* (semver) Unaffected: 6.12.95 , ≤ 6.12.* (semver) Unaffected: 6.18.38 , ≤ 6.18.* (semver) Unaffected: 7.1.3 , ≤ 7.1.* (semver) Unaffected: 7.2 , ≤ * (original_commit_for_fix)

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "block/blk-cgroup.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
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              "versionType": "git"
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              "versionType": "git"
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            {
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            {
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              "versionType": "git"
            },
            {
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              "version": "0f6090d90f627d8c58f939067d6c6821ce1b3c68",
              "versionType": "git"
            },
            {
              "lessThan": "6.4",
              "status": "affected",
              "version": "6.3.9",
              "versionType": "semver"
            }
          ]
        },
        {
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          "product": "Linux",
          "programFiles": [
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              "versionType": "semver"
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              "versionType": "semver"
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              "status": "unaffected",
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              "versionType": "semver"
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              "status": "unaffected",
              "version": "7.1.3",
              "versionType": "semver"
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              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
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      "cpeApplicability": [
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        }
      ],
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            "baseSeverity": "HIGH",
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            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Exploitation requires local cgroup management (rmdir on cgroupfs) and concurrent block I/O to populate per-blkcg rstat lists; the vulnerable code is in the block cgroup teardown path, not in any network protocol handler.\nAC:L - The attacker controls both sides of the race by issuing I/O on multiple block devices to create multiple blkgs with pending stats, then concurrently destroying the cgroup to trigger parallel blkg_release() calls on multiple CPUs.\nPR:L - Triggering cgroup deletion and block I/O requires only delegated cgroup write access or namespace/container root (CAP_SYS_ADMIN in a user namespace), not init-namespace root; this is routinely available in containers, Kubernetes pods, and systemd user cgroup hierarchies.\nUI:N - No victim interaction is required; the attacker programmatically performs I/O and cgroup teardown from their own process or container.\nS:U - The UAF corrupts kernel heap memory within the same kernel security domain; it does not inherently cross a VM, container, or IOMMU boundary without a separate privilege-escalation step.\nC:H - The use-after-free dereferences freed blkg structures and associated iostat data during list iteration, enabling arbitrary kernel memory read primitives typical of slab UAF bugs.\nI:H - UAF on kmalloc-allocated blkg objects allows heap grooming and write through dangling pointers, which can be leveraged for arbitrary kernel memory modification or code execution.\nA:H - Concurrent use-after-free during blkg teardown can cause immediate kernel oops/panic from accessing freed memory, and repeated triggering enables reliable denial of service."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T04:51:07.787Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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        {
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        },
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        },
        {
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        },
        {
          "url": "https://git.kernel.org/stable/c/afebe44facc48a61761e885bbb7f0380d4a603ec"
        },
        {
          "url": "https://git.kernel.org/stable/c/0ab5ee5a1badb58cbb2242617cb01a4972b1f2a2"
        }
      ],
      "title": "blk-cgroup: fix UAF in __blkcg_rstat_flush()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-63802",
    "datePublished": "2026-07-19T12:02:08.020Z",
    "dateReserved": "2026-07-19T07:54:57.013Z",
    "dateUpdated": "2026-08-17T04:51:07.787Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

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.

Action not permitted

FKIE_CVE-2026-63802

CVE-2026-63802 (GCVE-0-2026-63802)

Tags

Sightings

Nomenclature