CVE-2026-63955 (GCVE-0-2026-63955)

Vulnerability from cvelistv5 – Published: 2026-07-19 14:55 – Updated: 2026-08-05 12:37
VLAI
Title
mm/vmalloc: do not trigger BUG() on BH disabled context
Summary
In the Linux kernel, the following vulnerability has been resolved: mm/vmalloc: do not trigger BUG() on BH disabled context __get_vm_area_node() currently triggers a BUG() if in_interrupt() returns true. However, in_interrupt() also reports true when BH are disabled. The bridge code can call rhashtable_lookup_insert_fast() with bottom halves disabled: __vlan_add() -> br_fdb_add_local() spin_lock_bh(&br->hash_lock); <-- Disable BH -> fdb_add_local() -> fdb_create() -> rhashtable_lookup_insert_fast() -> kvmalloc() -> vmalloc() -> __get_vm_area_node() -> BUG_ON(in_interrupt()) spin_unlock_bh(&br->hash_lock) this triggers the BUG() despite the caller not being in NMI or hard IRQ context. Replace the in_interrupt() check with in_nmi() || in_hardirq().
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: c6307674ed82c0c57d6e1e3408e84ac449ab8e94 , < ad7eff07b625f53c3fb513b30d7a8c5a79fbc7ce (git)
Affected: c6307674ed82c0c57d6e1e3408e84ac449ab8e94 , < 04aa71da5f35aacdc9ae9cb5150947daa624f641 (git)
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Linux Linux Affected: 6.19
Unaffected: 0 , < 6.19 (semver)
Unaffected: 7.0.12 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "mm/vmalloc.c"
          ],
          "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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              "status": "affected",
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              "versionType": "git"
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          "vendor": "Linux",
          "versions": [
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              "status": "affected",
              "version": "6.19"
            },
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              "status": "unaffected",
              "version": "0",
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      "cpeApplicability": [
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          "nodes": [
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                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.0.12",
                  "versionStartIncluding": "6.19",
                  "vulnerable": true
                },
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                  "versionEndExcluding": "7.1",
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                  "vulnerable": true
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              "negate": false,
              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/vmalloc: do not trigger BUG() on BH disabled context\n\n__get_vm_area_node() currently triggers a BUG() if in_interrupt() returns\ntrue.  However, in_interrupt() also reports true when BH are disabled.\n\nThe bridge code can call rhashtable_lookup_insert_fast() with bottom\nhalves disabled:\n\n__vlan_add()\n -\u003e br_fdb_add_local()\n  spin_lock_bh(\u0026br-\u003ehash_lock); \u003c-- Disable BH\n   -\u003e fdb_add_local()\n    -\u003e fdb_create()\n     -\u003e rhashtable_lookup_insert_fast()\n      -\u003e kvmalloc()\n       -\u003e vmalloc()\n        -\u003e __get_vm_area_node()\n         -\u003e BUG_ON(in_interrupt())\n  spin_unlock_bh(\u0026br-\u003ehash_lock)\n\nthis triggers the BUG() despite the caller not being in NMI or\nhard IRQ context.\n\nReplace the in_interrupt() check with in_nmi() || in_hardirq()."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - After kvmalloc gained GFP_ATOMIC vmalloc fallback, reachable rhashtable resize paths run from network packet handling (e.g. bridge FDB learning in RX softirq, VXLAN UDP receive/snoop) and can call __get_vm_area_node() while in_interrupt() is true.\nAC:L - An attacker can reliably trigger the BUG by flooding a reachable bridge/VXLAN interface with many unique source MACs (or equivalent netlink admin operations) to force rhashtable growth and a large GFP_ATOMIC kvmalloc vmalloc fallback.\nPR:N - The highest-impact path needs no kernel privileges: sending crafted L2/overlay packets to a learning bridge or VXLAN endpoint is sufficient; netlink-only paths additionally require CAP_NET_ADMIN but are not the ceiling.\nUI:N - Exploitation is fully attacker-driven packet or netlink traffic and does not require any victim user action beyond normal system operation.\nS:U - Impact is a host kernel BUG/panic from the mm/vmalloc path; it does not cross a VM, IOMMU, or sandbox security boundary for privilege escalation.\nC:N - The failure mode is an intentional BUG_ON() kernel panic with no memory corruption, out-of-bounds access, or information disclosure primitive.\nI:N - No attacker-controlled memory is modified; the bug only aborts the kernel via BUG() rather than providing a write or code-execution primitive.\nA:H - Hitting BUG_ON(in_interrupt()) in __get_vm_area_node() causes a kernel BUG/oops/panic, producing total loss of system availability."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:37:39.551Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/ad7eff07b625f53c3fb513b30d7a8c5a79fbc7ce"
        },
        {
          "url": "https://git.kernel.org/stable/c/04aa71da5f35aacdc9ae9cb5150947daa624f641"
        }
      ],
      "title": "mm/vmalloc: do not trigger BUG() on BH disabled context",
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-63955",
    "datePublished": "2026-07-19T14:55:46.903Z",
    "dateReserved": "2026-07-19T07:54:57.023Z",
    "dateUpdated": "2026-08-05T12:37:39.551Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-63955",
      "date": "2026-09-21",
      "epss": "0.00468",
      "percentile": "0.39543"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "defaultStatus": "unaffected",
                "product": "Linux",
                "programFiles": [
                  "mm/vmalloc.c"
                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux",
                "versions": [
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                  },
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          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/vmalloc: do not trigger BUG() on BH disabled context\n\n__get_vm_area_node() currently triggers a BUG() if in_interrupt() returns\ntrue.  However, in_interrupt() also reports true when BH are disabled.\n\nThe bridge code can call rhashtable_lookup_insert_fast() with bottom\nhalves disabled:\n\n__vlan_add()\n -\u003e br_fdb_add_local()\n  spin_lock_bh(\u0026br-\u003ehash_lock); \u003c-- Disable BH\n   -\u003e fdb_add_local()\n    -\u003e fdb_create()\n     -\u003e rhashtable_lookup_insert_fast()\n      -\u003e kvmalloc()\n       -\u003e vmalloc()\n        -\u003e __get_vm_area_node()\n         -\u003e BUG_ON(in_interrupt())\n  spin_unlock_bh(\u0026br-\u003ehash_lock)\n\nthis triggers the BUG() despite the caller not being in NMI or\nhard IRQ context.\n\nReplace the in_interrupt() check with in_nmi() || in_hardirq()."
          }
        ],
        "id": "CVE-2026-63955",
        "lastModified": "2026-07-27T17:44:23.777",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 7.5,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "NONE",
                "integrityImpact": "NONE",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 3.9,
              "impactScore": 3.6,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-07-19T16:17:14.307",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/04aa71da5f35aacdc9ae9cb5150947daa624f641"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/ad7eff07b625f53c3fb513b30d7a8c5a79fbc7ce"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Awaiting Analysis"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-08-21T16:47:15+00:00",
      "cve": "CVE-2026-63955",
      "id": "CVE-2026-63955",
      "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: mm/vmalloc: do not trigger BUG() on BH disabled context",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63955.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-07-21T13:02:48Z",
      "cve": "CVE-2026-63955",
      "id": "CVE-2026-63955",
      "initial_release_date": "2026-07-21T13:02:48Z",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-63955",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-63955.json",
      "version": "2"
    }
  }
}



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  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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