CVE-2026-68462 (GCVE-0-2026-68462)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:51 – Updated: 2026-08-17 05:39
VLAI
Title
bpf: Reject negative const offsets for buffer pointers
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Reject negative const offsets for buffer pointers The verifier rejects variable offsets for PTR_TO_TP_BUFFER and PTR_TO_BUF accesses, but it currently accepts a constant negative offset produced by pointer arithmetic. Commit 022ac0750883 ("bpf: use reg->var_off instead of reg->off for pointers") moved constant pointer offsets from reg->off to reg->var_off. However, __check_buffer_access() continued to check only the instruction offset. An access with reg->var_off equal to -8 and an instruction offset of zero therefore passes verification. For writable raw tracepoints, the access end is also calculated from the unsigned reg->var_off.value. An eight-byte access starting at -8 wraps the calculated end to zero, allowing the program to load and attach without increasing max_tp_access. After ensuring that reg->var_off is constant, calculate the effective access start using signed arithmetic and reject it when it is negative. Use the validated start to calculate the access end for both PTR_TO_TP_BUFFER and PTR_TO_BUF.
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: 022ac075088366b62e130da5e1b200bc93a47191 , < 314bd592085c0720ef519f6edbc5f41440ff78d4 (git)
Affected: 022ac075088366b62e130da5e1b200bc93a47191 , < fd4cfa8c8f9a17cdec0539334d28754bc1d8a5d9 (git)
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Linux Linux Affected: 7.1
Unaffected: 0 , < 7.1 (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/bpf/verifier.c"
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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      "descriptions": [
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Reject negative const offsets for buffer pointers\n\nThe verifier rejects variable offsets for PTR_TO_TP_BUFFER and PTR_TO_BUF\naccesses, but it currently accepts a constant negative offset produced by\npointer arithmetic.\n\nCommit 022ac0750883 (\"bpf: use reg-\u003evar_off instead of reg-\u003eoff for\npointers\") moved constant pointer offsets from reg-\u003eoff to reg-\u003evar_off.\nHowever, __check_buffer_access() continued to check only the instruction\noffset. An access with reg-\u003evar_off equal to -8 and an instruction offset\nof zero therefore passes verification.\n\nFor writable raw tracepoints, the access end is also calculated from the\nunsigned reg-\u003evar_off.value. An eight-byte access starting at -8 wraps\nthe calculated end to zero, allowing the program to load and attach\nwithout increasing max_tp_access.\n\nAfter ensuring that reg-\u003evar_off is constant, calculate the effective\naccess start using signed arithmetic and reject it when it is negative.\nUse the validated start to calculate the access end for both\nPTR_TO_TP_BUFFER and PTR_TO_BUF."
        }
      ],
      "metrics": [
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            "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": [
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              "lang": "en",
              "value": "AV:L - The bug is in bpf_check() during bpf(BPF_PROG_LOAD); the path is bpf_prog_load() \u2192 bpf_check() \u2192 check_mem_access() \u2192 __check_buffer_access() on PTR_TO_TP_BUFFER/PTR_TO_BUF. Per kernel CNA guidance BPF verifier bugs are Local, not network-reachable.\nAC:L - Exploitation is deterministic: pointer arithmetic (e.g. r6 += -8) yields a constant negative reg-\u003evar_off that passes the insn-only check, and unsigned wrap sets max_tp_access/max_rdwr_access to zero. The attacker fully controls program bytecode and triggering with no race or layout dependency.\nPR:L - Affected BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE and BPF_PROG_TYPE_TRACING/BPF_TRACE_ITER programs require CAP_BPF and CAP_PERFMON checked by bpf_token_capable(); BPF tokens delegate these capabilities into a non-init user namespace, so a namespace-local actor can reach bpf_prog_load without init-namespace root.\nUI:N - No victim interaction is required; after loading and attaching the malicious program the attacker triggers execution by reading a BPF iterator fd or causing a writable raw tracepoint to fire, entirely through their own syscalls.\nS:U - The verifier bypass permits out-of-bounds kernel reads/writes adjacent to tracepoint or iterator buffers within the same host kernel security authority; impact is standard kernel memory corruption and privilege escalation, not a VM, container, or IOMMU boundary crossing.\nC:H - Verified loads at negative offsets read up to eight bytes before PTR_TO_TP_BUFFER or PTR_TO_BUF targets, disclosing adjacent kernel stack or kmalloc memory (map keys/values, tracepoint writable buffers); per guidance out-of-bounds kernel reads warrant High confidentiality impact.\nI:H - Writable raw tracepoint programs can store at negative offsets while max_tp_access wraps to zero, and PTR_TO_BUF iterator contexts allow verified writes before map value buffers; these out-of-bounds stores corrupt adjacent kernel memory with a plausible control-flow hijack primitive.\nA:H - Out-of-bounds kernel memory accesses from attached BPF programs commonly provoke kernel oops or panic; the attacker can repeatedly trigger iterator reads or writable raw tracepoints to deny host availability."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T05:39:09.532Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/314bd592085c0720ef519f6edbc5f41440ff78d4"
        },
        {
          "url": "https://git.kernel.org/stable/c/fd4cfa8c8f9a17cdec0539334d28754bc1d8a5d9"
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      ],
      "title": "bpf: Reject negative const offsets for buffer pointers",
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-68462",
    "datePublished": "2026-08-15T05:51:21.948Z",
    "dateReserved": "2026-07-30T09:28:09.395Z",
    "dateUpdated": "2026-08-17T05:39:09.532Z",
    "state": "PUBLISHED"
  },
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      "date": "2026-08-24",
      "epss": "0.0012",
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-17T15:00:08+00:00",
      "cve": "CVE-2026-68462",
      "id": "CVE-2026-68462",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: bpf: Reject negative const offsets for buffer pointers",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-68462.json",
      "version": "3"
    }
  }
}



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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.

Sightings

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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.
  • 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.