CVE-2026-89579 (GCVE-0-2026-89579)
Vulnerability from cvelistv5
Published
2026-09-11 19:44
Modified
2026-10-19 08:49
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: bpf: Harden bloom filter sizing and indexing on 32-bit kernels bloom_map_alloc() has two 32-bit-specific problems when the computed bitmap reaches the U32_MAX fallback case. First, BITS_TO_BYTES(U32_MAX) is evaluated with 32-bit arithmetic. The addition performed by DIV_ROUND_UP wraps, so the map allocates only the fixed-size bloom filter object while keeping bitset_mask == U32_MAX. Subsequent updates can then write past the allocated object. Second, fixing only the allocation size is not sufficient. The bloom hash is a u32, but set_bit() takes a signed long bit number and x86 test_bit() eventually feeds the index to variable_test_bit(long, ...). On 32-bit kernels, hashes in [0x80000000, U32_MAX] therefore become negative bit offsets. x86 bt/bts with a memory operand interpret those offsets relative to the supplied base, so a map with bitset_mask == U32_MAX can read or write before bloom->bitset even after allocating the full 512 MiB bitmap. Keep the U32_MAX fallback, but split each hash into a word pointer and an in-word bit number before calling test_bit() or set_bit(). The bitops argument is then always in [0, BITS_PER_LONG - 1], while BIT_WORD(h) still selects the intended word in the full bitmap. Compute the bitset size from (u64)bitset_mask + 1 before passing the final size to bpf_map_area_alloc(). This fixes the original under-allocation and keeps the allocated storage consistent with the addressable bitset. Exploitation note: local privilege escalation is possible on a 32-bit x86 kernel using the under-allocation bug from a binary with CAP_BPF.
References
Impacted products
Vendor Product Version
Linux Linux Version: 9330986c03006ab1d33d243b7cfe598a7a3c1baa
Version: 9330986c03006ab1d33d243b7cfe598a7a3c1baa
Version: 9330986c03006ab1d33d243b7cfe598a7a3c1baa
Version: 9330986c03006ab1d33d243b7cfe598a7a3c1baa
Version: 9330986c03006ab1d33d243b7cfe598a7a3c1baa
Version: 9330986c03006ab1d33d243b7cfe598a7a3c1baa
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/bpf/bloom_filter.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/bpf/bloom_filter.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.16"
            },
            {
              "lessThan": "5.16",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.188",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.157",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.109",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.188",
                  "versionStartIncluding": "5.16",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.157",
                  "versionStartIncluding": "5.16",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.109",
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                  "versionEndExcluding": "6.18.50",
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                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "versionStartIncluding": "5.16",
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
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                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Harden bloom filter sizing and indexing on 32-bit kernels\n\nbloom_map_alloc() has two 32-bit-specific problems when the computed\nbitmap reaches the U32_MAX fallback case.\n\nFirst, BITS_TO_BYTES(U32_MAX) is evaluated with 32-bit arithmetic. The\naddition performed by DIV_ROUND_UP wraps, so the map allocates only the\nfixed-size bloom filter object while keeping bitset_mask == U32_MAX.\nSubsequent updates can then write past the allocated object.\n\nSecond, fixing only the allocation size is not sufficient. The bloom hash\nis a u32, but set_bit() takes a signed long bit number and x86 test_bit()\neventually feeds the index to variable_test_bit(long, ...). On 32-bit\nkernels, hashes in [0x80000000, U32_MAX] therefore become negative bit\noffsets. x86 bt/bts with a memory operand interpret those offsets relative\nto the supplied base, so a map with bitset_mask == U32_MAX can read or\nwrite before bloom-\u003ebitset even after allocating the full 512 MiB bitmap.\n\nKeep the U32_MAX fallback, but split each hash into a word pointer and an\nin-word bit number before calling test_bit() or set_bit(). The bitops\nargument is then always in [0, BITS_PER_LONG - 1], while BIT_WORD(h) still\nselects the intended word in the full bitmap.\n\nCompute the bitset size from (u64)bitset_mask + 1 before passing the final\nsize to bpf_map_area_alloc(). This fixes the original under-allocation and\nkeeps the allocated storage consistent with the addressable bitset.\n\nExploitation note: local privilege escalation is possible on a 32-bit x86\nkernel using the under-allocation bug from a binary with CAP_BPF."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The bug is reached only via local bpf(2) syscalls: BPF_MAP_CREATE of BPF_MAP_TYPE_BLOOM_FILTER, then BPF_MAP_UPDATE_ELEM/LOOKUP_ELEM which call bloom_map_push_elem/peek_elem. Per kernel CNA guidance BPF is Local, not network-reachable.\nAC:L - On a 32-bit kernel the attacker deterministically forces the U32_MAX bitmap fallback with a large max_entries so BITS_TO_BYTES wraps and under-allocates; BPF_F_ZERO_SEED and chosen values then drive set_bit/test_bit to selected out-of-bounds indexes with no race or uncontrolled layout.\nPR:L - Creating a bloom-filter map requires CAP_BPF in map_create_alloc (bpf_token_capable). Per kernel guidance this is Low because CAP_BPF is obtainable via user namespaces and BPF token delegation, not only init-namespace root.\nUI:N - The attacker creates the undersized bloom map and issues lookup/update syscalls from their own process; no victim action such as mounting a filesystem or opening a file is required.\nS:U - The out-of-bounds bit set/test corrupts kernel heap around the undersized bloom object on the same host. This is standard kernel memory corruption and privilege escalation, not a VM escape or IOMMU boundary bypass.\nC:H - With bitset_mask==U32_MAX and a near-empty allocation, bloom_map_peek_elem\u0027s test_bit is an out-of-bounds kernel bit-read oracle, and the matching OOB writes enable heap disclosure; kernel guidance rates such memory corruption as High confidentiality impact.\nI:H - bloom_map_push_elem\u0027s set_bit writes past (and on 32-bit x86, before) the allocated object across a huge range, a controllable OOB write. The fix commit documents local privilege escalation from CAP_BPF on 32-bit x86.\nA:H - The same unbounded set_bit/test_bit indexes unmapped pages around the undersized kmalloc object and reliably produces a kernel oops or panic, which is High availability impact per kernel guidance."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:49:12.203Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/a6183bc683f97f4317f7e84939ca7fff37c5688b"
        },
        {
          "url": "https://git.kernel.org/stable/c/80551bf8912c42d1e3d55eec6fa3c40f306c3de8"
        },
        {
          "url": "https://git.kernel.org/stable/c/3b7a13eccfcf97714ffc1ca6aa663d66d4a30e29"
        },
        {
          "url": "https://git.kernel.org/stable/c/272fcb4ba6fab678db0eb966dc81c4c804bef64a"
        },
        {
          "url": "https://git.kernel.org/stable/c/dff481e12b3f127739f6a4ea7cef2c25dc12e056"
        },
        {
          "url": "https://git.kernel.org/stable/c/11c1e836710dcba03e50454a4eedfdbaf8d3050e"
        }
      ],
      "title": "bpf: Harden bloom filter sizing and indexing on 32-bit kernels",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89579",
    "datePublished": "2026-09-11T19:44:46.110Z",
    "dateReserved": "2026-09-11T19:38:34.728Z",
    "dateUpdated": "2026-10-19T08:49:12.203Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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