CVE-2026-72111 (GCVE-0-2026-72111)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:52 – Updated: 2026-08-17 05:40
VLAI
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.
Severity
8.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 5d99e198be279045e6ecefe220f5c52f8ce9bfd5 , < bde92f65042ec14389782dd223f706bf6b59ce5d (git)
Affected: 5d99e198be279045e6ecefe220f5c52f8ce9bfd5 , < 0993dc5fc619c0b25ab1310cb11d65e78351c0fe (git)
Affected: 5d99e198be279045e6ecefe220f5c52f8ce9bfd5 , < 5a55f9aecc08990940e70f0c7048a80850c5a16a (git)
Affected: 5d99e198be279045e6ecefe220f5c52f8ce9bfd5 , < 5e0b273e0a62cc04ec338c7b502797c66c2ed42a (git)
Affected: 1050727d83e70449991c29dd1cf29fe936a63da3 (git)
Affected: 27ca3e20fe80be85a92b10064dfeb56cb2564b1c (git)
Affected: 6.10.13 , < 6.11 (semver)
Affected: 6.11.2 , < 6.12 (semver)
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Linux Linux Affected: 6.12
Unaffected: 0 , < 6.12 (semver)
Unaffected: 6.12.103 , ≤ 6.12.* (semver)
Unaffected: 6.18.40 , ≤ 6.18.* (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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              "operator": "OR"
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Reset register bounds before narrowing retval range in check_mem_access()\n\nWhen the BPF verifier processes a context load of an LSM hook return\nvalue, it calls __mark_reg_s32_range() to narrow the register to the\nhook\u0027s valid range. However, __mark_reg_s32_range() intersects the new\nrange with the register\u0027s existing bounds using max_t()/min_t() rather\nthan replacing them.\n\nIf the destination register carries stale bounds from a prior instruction\n(e.g. BPF_MOV64_IMM), the intersection can produce a range narrower than\nreality. The verifier then believes it knows the register\u0027s exact value,\nwhile at runtime the actual hook return value is loaded, creating a\nverifier/runtime mismatch that can be used to bypass BPF memory safety\nchecks.\n\nThe else branch already calls mark_reg_unknown() to reset register state\nbefore any narrowing. Apply the same reset in the is_retval path so\nstale bounds are cleared before __mark_reg_s32_range() intersects."
        }
      ],
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            "baseSeverity": "HIGH",
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              "value": "AV:L - The flaw is reached only through bpf(BPF_PROG_LOAD) during bpf_check()-\u003echeck_mem_access() when a BPF_LSM_MAC program loads the LSM hook return value from PTR_TO_CTX; per kernel CNA guidance BPF verifier issues are Local even if attached programs later run on file, socket, or network LSM hooks.\nAC:L - An attacker fully controls the BPF instruction sequence (e.g., BPF_MOV64_IMM to leave stale bounds, then a ctx retval load) and can deterministically force __mark_reg_s32_range() to intersect into an overly narrow range without races, special memory layout, or other uncontrollable conditions.\nPR:L - Loading BPF_PROG_TYPE_LSM programs requires CAP_BPF and CAP_PERFMON (is_perfmon_prog_type), both blocked for unprivileged users when kernel.unprivileged_bpf_disabled is set but obtainable inside user namespaces on typical CONFIG_BPF_LSM systems per kernel CNA BPF guidance.\nUI:N - No victim interaction is required; the attacker loads, verifies, and attaches their own malicious BPF LSM program and triggers the attached LSM hook with their own local syscalls or network operations.\nS:C - A container or user-namespace tenant with namespace-granted CAP_BPF can load a verifier-bypassing BPF LSM program whose runtime memory corruption executes in host kernel context on LSM hook firing, crossing the container-to-host security boundary on multi-tenant cloud and Android-style deployments.\nC:H - The verifier/runtime register-bounds mismatch lets unsafe BPF programs pass verification and perform out-of-bounds reads on ctx, stack, or map memory at runtime, a memory-corruption primitive that can be developed into arbitrary kernel memory disclosure.\nI:H - False exact-knowledge of the LSM return-value register enables verifier-approved pointer arithmetic and memory writes that are invalid at runtime, enabling out-of-bounds writes and control-flow hijacking toward arbitrary kernel code execution from BPF context.\nA:H - Running verifier-incorrect BPF LSM programs can trigger kernel oops or panic from corrupted memory accesses, and once attached the attacker can repeatedly invoke the hook to cause repeatable host-wide denial of service."
            }
          ]
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        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-72111",
    "datePublished": "2026-08-15T05:52:52.538Z",
    "dateReserved": "2026-08-09T03:40:39.906Z",
    "dateUpdated": "2026-08-17T05:40:25.647Z",
    "state": "PUBLISHED"
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      "date": "2026-09-21",
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      "percentile": "0.07395"
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Reset register bounds before narrowing retval range in check_mem_access()\n\nWhen the BPF verifier processes a context load of an LSM hook return\nvalue, it calls __mark_reg_s32_range() to narrow the register to the\nhook\u0027s valid range. However, __mark_reg_s32_range() intersects the new\nrange with the register\u0027s existing bounds using max_t()/min_t() rather\nthan replacing them.\n\nIf the destination register carries stale bounds from a prior instruction\n(e.g. BPF_MOV64_IMM), the intersection can produce a range narrower than\nreality. The verifier then believes it knows the register\u0027s exact value,\nwhile at runtime the actual hook return value is loaded, creating a\nverifier/runtime mismatch that can be used to bypass BPF memory safety\nchecks.\n\nThe else branch already calls mark_reg_unknown() to reset register state\nbefore any narrowing. Apply the same reset in the is_retval path so\nstale bounds are cleared before __mark_reg_s32_range() intersects."
          }
        ],
        "id": "CVE-2026-72111",
        "lastModified": "2026-08-17T06:18:10.280",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 8.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "CHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-17T22:30:40+00:00",
      "cve": "CVE-2026-72111",
      "id": "CVE-2026-72111",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_affected": "184",
      "product_status:known_not_affected": "90",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: bpf: Reset register bounds before narrowing retval range in check_mem_access()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-72111.json",
      "version": "3"
    },
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      "aggregate_severity": "moderate",
      "current_release_date": "2026-08-28T16:40:33Z",
      "cve": "CVE-2026-72111",
      "id": "CVE-2026-72111",
      "initial_release_date": "2026-08-28T16:40:33Z",
      "product_status:known_affected": "111",
      "product_status:known_not_affected": "251",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-72111",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-72111.json",
      "version": "2"
    }
  }
}



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