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bpf: Reset register bounds before narrowing retval range in check_mem_access()

Type: advisorySources: OSV

In the Linux kernel, the following vulnerability has been resolved: bpf: Reset register bounds before narrowing retval range in check_mem_access() When the BPF verifier processes a context load of an LSM hook return value, it calls __mark_reg_s32_range() to narrow the register to the hook's valid range. However, __mark_reg_s32_range() intersects the new range with the register's existing bounds using max_t()/min_t() rather than replacing them. If the destination register carries stale bounds from a prior instruction (e.g. BPF_MOV64_IMM), the intersection can produce a range narrower than reality. The verifier then believes it knows the register's exact value, while at runtime the actual hook return value is loaded, creating a verifier/runtime mismatch that can be used to bypass BPF memory safety checks. The else branch already calls mark_reg_unknown() to reset register state before any narrowing. Apply the same reset in the is_retval path so stale bounds are cleared before __mark_reg_s32_range() intersects.

Products
Kernel
Affected versions
Not specified
Fixed versions
6.12.103, 6.18.40, 7.1.5
CVEs
CVE-2026-72111
Confirmed fixed CVEs
Not specified
Updated in this feed
7 Nov 2026, 13:12 UTC · Revision 1

Source evidence

bpf: Reset register bounds before narrowing retval range in check_mem_access()

core-osv · Original source

Published 15 Aug 2026, 05:52 UTC

In the Linux kernel, the following vulnerability has been resolved: bpf: Reset register bounds before narrowing retval range in check_mem_access() When the BPF verifier processes a context load of an LSM hook return value, it calls __mark_reg_s32_range() to narrow the register to the hook's valid range. However, __mark_reg_s32_range() intersects the new range with the register's existing bounds using max_t()/min_t() rather than replacing them. If the destination register carries stale bounds from a prior instruction (e.g. BPF_MOV64_IMM), the intersection can produce a range narrower than reality. The verifier then believes it knows the register's exact value, while at runtime the actual hook return value is loaded, creating a verifier/runtime mismatch that can be used to bypass BPF memory safety checks. The else branch already calls mark_reg_unknown() to reset register state before any narrowing. Apply the same reset in the is_retval path so stale bounds are cleared before __mark_reg_s32_range() intersects.

osv:CVE-2026-72111

Kernel

Fixed versions: 6.12.103, 6.18.40, 7.1.5

Complete source record
{
  "id": "ab4ac7cc60b11c89d2441cbbb6b9a15b466d0a6ed6b3e1843a10e4d1f8c0dec0",
  "url": "https://osv.dev/vulnerability/CVE-2026-72111",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "bpf: Reset register bounds before narrowing retval range in check_mem_access()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: bpf: Reset register bounds before narrowing retval range in check_mem_access() When the BPF verifier processes a context load of an LSM hook return value, it calls __mark_reg_s32_range() to narrow the register to the hook's valid range. However, __mark_reg_s32_range() intersects the new range with the register's existing bounds using max_t()/min_t() rather than replacing them. If the destination register carries stale bounds from a prior instruction (e.g. BPF_MOV64_IMM), the intersection can produce a range narrower than reality. The verifier then believes it knows the register's exact value, while at runtime the actual hook return value is loaded, creating a verifier/runtime mismatch that can be used to bypass BPF memory safety checks. The else branch already calls mark_reg_unknown() to reset register state before any narrowing. Apply the same reset in the is_retval path so stale bounds are cleared before __mark_reg_s32_range() intersects.",
    "evidence": "osv:CVE-2026-72111",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.12.103",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.40",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.1.5",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-72111",
      "aliases": [
        "CVE-2026-72111"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
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              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
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                {
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                {
                  "fixed": "5a55f9aecc08990940e70f0c7048a80850c5a16a"
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                  "fixed": "5e0b273e0a62cc04ec338c7b502797c66c2ed42a"
                }
              ]
            },
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "6.10.13"
                },
                {
                  "fixed": "6.11"
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            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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            {
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            {
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          "versions": [
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            "v6.11.7",
            "v6.11.6",
            "v6.11.5",
            "v6.11.4",
            "v6.11.3",
            "v6.11.2"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-72111.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
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                  "introduced": "6.12.0"
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              ]
            },
            {
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                {
                  "fixed": "6.18.40"
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              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.1.5"
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          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-72111.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:50.633857610Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/0993dc5fc619c0b25ab1310cb11d65e78351c0fe",
        "https://git.kernel.org/stable/c/5a55f9aecc08990940e70f0c7048a80850c5a16a",
        "https://git.kernel.org/stable/c/5e0b273e0a62cc04ec338c7b502797c66c2ed42a",
        "https://git.kernel.org/stable/c/bde92f65042ec14389782dd223f706bf6b59ce5d",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72111.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-72111",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72111.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-72111",
        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 519412,
  "published_at": "2026-08-15T05:52:52.538+00:00"
}