CVE-2026-93125 (GCVE-0-2026-93125)

Vulnerability from cvelistv5 – Published: 2026-09-17 16:11 – Updated: 2026-09-18 17:56
VLAI
Title
bpf: Reject rdonly/rdwr_buf_size kfunc arguments that exceed u32 max
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Reject rdonly/rdwr_buf_size kfunc arguments that exceed u32 max check_kfunc_args() detects a kfunc argument named rdonly_buf_size or rdwr_buf_size and stores reg->var_off.value into meta->r0_size, a u64, and does not bound it. check_kfunc_call() later copies that value into the returned register's mem_size field: meta->r0_size = reg->var_off.value; ... regs[BPF_REG_0].mem_size = meta.r0_size; regs[BPF_REG_0].mem_size is u32. A constant whose upper 32 bits are set gets truncated instead of causing a load-time rejection, so the verifier records a PTR_TO_MEM register with an approximately 4 GiB mem_size for whatever allocation the kfunc returned. A later access check against that register uses the truncated, wrong bound. Reject rdonly_buf_size/rdwr_buf_size values that exceed U32_MAX at the point meta->r0_size is set.
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: eb1f7f71c126c8fd50ea81af98f97c4b581ea4ae , < 56a3846830ac95a472297d0cbba75cbff29540bb (git)
Affected: eb1f7f71c126c8fd50ea81af98f97c4b581ea4ae , < 2aaf67f0516fde29620d0edfc29c01b9ea7ad430 (git)
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Linux Linux Affected: 6.1
Unaffected: 0 , < 6.1 (semver)
Unaffected: 7.2.6 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/bpf/verifier.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "56a3846830ac95a472297d0cbba75cbff29540bb",
              "status": "affected",
              "version": "eb1f7f71c126c8fd50ea81af98f97c4b581ea4ae",
              "versionType": "git"
            },
            {
              "lessThan": "2aaf67f0516fde29620d0edfc29c01b9ea7ad430",
              "status": "affected",
              "version": "eb1f7f71c126c8fd50ea81af98f97c4b581ea4ae",
              "versionType": "git"
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          "product": "Linux",
          "programFiles": [
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.1"
            },
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
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              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.6",
                  "versionStartIncluding": "6.1",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3-rc1",
                  "versionStartIncluding": "6.1",
                  "vulnerable": true
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              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Reject rdonly/rdwr_buf_size kfunc arguments that exceed u32 max\n\ncheck_kfunc_args() detects a kfunc argument named rdonly_buf_size or\nrdwr_buf_size and stores reg-\u003evar_off.value into meta-\u003er0_size, a u64,\nand does not bound it. check_kfunc_call() later copies that value into\nthe returned register\u0027s mem_size field:\n\n  meta-\u003er0_size = reg-\u003evar_off.value;\n  ...\n  regs[BPF_REG_0].mem_size = meta.r0_size;\n\nregs[BPF_REG_0].mem_size is u32. A constant whose upper 32 bits are set\ngets truncated instead of causing a load-time rejection, so the verifier\nrecords a PTR_TO_MEM register with an approximately 4 GiB mem_size for\nwhatever allocation the kfunc returned. A later access check against\nthat register uses the truncated, wrong bound.\n\nReject rdonly_buf_size/rdwr_buf_size values that exceed U32_MAX at the\npoint meta-\u003er0_size is set."
        }
      ],
      "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 - check_kfunc_args() takes the oversized rdonly_buf_size/rdwr_buf_size from the BPF program\u0027s own constant (reg-\u003evar_off.value) on the local bpf(BPF_PROG_LOAD) path (bpf_prog_load \u2192 bpf_check \u2192 check_kfunc_call). That immediate is not a field of a received packet or a ksmbd/nfsd message.\nAC:L - The attacker picks a 64-bit immediate with upper bits set (e.g. ~0ULL as in hid_rdesc_fixup_get_data_overflow) as the rdonly_buf_size/rdwr_buf_size argument; tnum_is_const succeeds and regs[BPF_REG_0].mem_size = meta.r0_size truncates deterministically, with no race or layout outside their control.\nPR:L - do_check_common() rejects BPF_PSEUDO_KFUNC_CALL unless env-\u003ebpf_capable, which bpf_check() sets from bpf_token_capable(token, CAP_BPF). CAP_BPF is a reduced capability and is delegable into a user namespace via a BPF token, so init-namespace root is not required.\nUI:N - The attacker loads the crafted program with bpf(BPF_PROG_LOAD) and runs it themselves via BPF_PROG_TEST_RUN or by attaching their own HID-BPF/io_uring struct_ops. No separate victim action such as mounting an image is required.\nS:U - The truncated PTR_TO_MEM mem_size lets the verified program read and write host kernel memory, which is a standard kernel privilege escalation in the same authority. It does not cross a KVM/Xen, IOMMU, or guest-to-host boundary.\nC:H - check_kfunc_call() copies the truncated r0_size into a PTR_TO_MEM register, so check_mem_region_access() allows loads of up to ~4 GiB. bpf_kfunc_call_test_get_rdonly_mem takes const int rdonly_buf_size: a value such as 0x1FFFFFFFF becomes -1, the size \u003e 8 check fails open, and the 8-byte prog_test_ref_kfunc is treated as a 4 GiB readable buffer.\nI:H - rdwr_buf_size kfuncs (bpf_kfunc_call_test_get_rdwr_mem, hid_bpf_get_data, bpf_io_uring_get_region) mark R0 as writable PTR_TO_MEM. The same truncated mem_size lets check_mem_region_access() accept stores past the real object, which is an arbitrary kernel write.\nA:H - Those verifier-allowed out-of-bounds loads and stores overrun the kfunc\u0027s actual object (prog_test_struct from get_mem, hid_bpf_get_data\u0027s ctx_kern-\u003edata, or an io_uring mapped region) and can oops or panic the kernel."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-18T17:56:05.805Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/56a3846830ac95a472297d0cbba75cbff29540bb"
        },
        {
          "url": "https://git.kernel.org/stable/c/2aaf67f0516fde29620d0edfc29c01b9ea7ad430"
        }
      ],
      "title": "bpf: Reject rdonly/rdwr_buf_size kfunc arguments that exceed u32 max",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-93125",
    "datePublished": "2026-09-17T16:11:29.895Z",
    "dateReserved": "2026-09-17T16:02:15.087Z",
    "dateUpdated": "2026-09-18T17:56:05.805Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-93125",
      "date": "2026-09-25",
      "epss": "0.00165",
      "percentile": "0.05081"
    },
    "microsoft_vex": {
      "current_release_date": "2026-09-24T02:12:43.000Z",
      "cve": "CVE-2026-93125",
      "id": "msrc_CVE-2026-93125",
      "initial_release_date": "2026-09-19T01:03:52.000Z",
      "product_status:known_affected": "3",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "bpf: Reject rdonly/rdwr_buf_size kfunc arguments that exceed u32 max",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-93125.json",
      "version": "4"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "defaultStatus": "unaffected",
                "product": "Linux",
                "programFiles": [
                  "kernel/bpf/verifier.c"
                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux",
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                    "status": "affected",
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                    "versionType": "git"
                  },
                  {
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                "vendor": "Linux",
                "versions": [
                  {
                    "status": "affected",
                    "version": "6.1"
                  },
                  {
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                    "status": "unaffected",
                    "version": "0",
                    "versionType": "semver"
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                  {
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                    "status": "unaffected",
                    "version": "7.2.6",
                    "versionType": "semver"
                  },
                  {
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                    "status": "unaffected",
                    "version": "7.3-rc1",
                    "versionType": "original_commit_for_fix"
                  }
                ]
              }
            ],
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Reject rdonly/rdwr_buf_size kfunc arguments that exceed u32 max\n\ncheck_kfunc_args() detects a kfunc argument named rdonly_buf_size or\nrdwr_buf_size and stores reg-\u003evar_off.value into meta-\u003er0_size, a u64,\nand does not bound it. check_kfunc_call() later copies that value into\nthe returned register\u0027s mem_size field:\n\n  meta-\u003er0_size = reg-\u003evar_off.value;\n  ...\n  regs[BPF_REG_0].mem_size = meta.r0_size;\n\nregs[BPF_REG_0].mem_size is u32. A constant whose upper 32 bits are set\ngets truncated instead of causing a load-time rejection, so the verifier\nrecords a PTR_TO_MEM register with an approximately 4 GiB mem_size for\nwhatever allocation the kfunc returned. A later access check against\nthat register uses the truncated, wrong bound.\n\nReject rdonly_buf_size/rdwr_buf_size values that exceed U32_MAX at the\npoint meta-\u003er0_size is set."
          }
        ],
        "id": "CVE-2026-93125",
        "lastModified": "2026-09-18T18:18:21.907",
        "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"
              },
              "exploitabilityScore": 1.8,
              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-09-17T17:18:07.247",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/2aaf67f0516fde29620d0edfc29c01b9ea7ad430"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/56a3846830ac95a472297d0cbba75cbff29540bb"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    }
  }
}



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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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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.
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  • 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.



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.