CVE-2026-90153 (GCVE-0-2026-90153)

Vulnerability from cvelistv5 – Published: 2026-09-17 16:06 – Updated: 2026-09-18 17:53
VLAI
Title
ksmbd: bound smb_check_perm_dacl() ACE walks by DACL size
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: bound smb_check_perm_dacl() ACE walks by DACL size smb_check_perm_dacl() validates that the DACL fits inside the NT security descriptor, but then bounds its two ACE walks by the remaining NTSD length (acl_size) rather than the DACL's declared size (pdacl_size). When pdacl->size is smaller than the trailing NTSD buffer, bytes after the declared DACL boundary - still inside the stored security descriptor - are parsed as ACEs during access checks. A crafted DACL can place an access-granting ACE beyond pdacl->size, and the current code accepts it during SMB2_CREATE access validation, while parse_dacl() and smb_inherit_dacl() stop at pdacl_size. Bound both ACE walks by pdacl_size to match the DACL boundary semantics used elsewhere in the server. Validation: - semantic KUnit harness shows the post-boundary ACE is selected before the fix and rejected (EACCES) after it - linux master (7.2-rc6), x86_64
Severity
8.1 (High)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 8f0541186e9ad1b62accc9519cc2b7a7240272a7 , < a2051ffe452afad52f580b85a3fd8851933b1e7c (git)
Affected: 8f0541186e9ad1b62accc9519cc2b7a7240272a7 , < a29f57a14c939586d84d7fd6a029bd1fd170098f (git)
Affected: 8f0541186e9ad1b62accc9519cc2b7a7240272a7 , < a4a307d149327dad5fb25187e1b03cebd1b04de6 (git)
Affected: 8f0541186e9ad1b62accc9519cc2b7a7240272a7 , < 8e4f75e979c1d9a51b0a48ac33d0cfd5f039ec67 (git)
Affected: 8f0541186e9ad1b62accc9519cc2b7a7240272a7 , < 79decd88dd3f0d42e7fb0689b1a7853bfa302459 (git)
Affected: cb69d4d6f709f87c94afa28ae64c501576692171 (git)
Affected: 6e8f4abf584253cbaa596ea4ad13110cf61cd4c9 (git)
Affected: 8e33102309bd6839b2e2e158f93a7b378cb4655d (git)
Affected: 5.15.62 , < 5.16 (semver)
Affected: 5.18.18 , < 5.19 (semver)
Affected: 5.19.2 , < 5.20 (semver)
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Linux Linux Affected: 6.0
Unaffected: 0 , < 6.0 (semver)
Unaffected: 6.6.157 , ≤ 6.6.* (semver)
Unaffected: 6.12.110 , ≤ 6.12.* (semver)
Unaffected: 6.18.52 , ≤ 6.18.* (semver)
Unaffected: 7.2.6 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)
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{
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: bound smb_check_perm_dacl() ACE walks by DACL size\n\nsmb_check_perm_dacl() validates that the DACL fits inside the NT\nsecurity descriptor, but then bounds its two ACE walks by the\nremaining NTSD length (acl_size) rather than the DACL\u0027s declared\nsize (pdacl_size).\n\nWhen pdacl-\u003esize is smaller than the trailing NTSD buffer, bytes\nafter the declared DACL boundary - still inside the stored security\ndescriptor - are parsed as ACEs during access checks.  A crafted\nDACL can place an access-granting ACE beyond pdacl-\u003esize, and the\ncurrent code accepts it during SMB2_CREATE access validation, while\nparse_dacl() and smb_inherit_dacl() stop at pdacl_size.\n\nBound both ACE walks by pdacl_size to match the DACL boundary\nsemantics used elsewhere in the server.\n\nValidation:\n- semantic KUnit harness shows the post-boundary ACE is selected\n  before the fix and rejected (EACCES) after it\n- linux master (7.2-rc6), x86_64"
        }
      ],
      "metrics": [
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The crafted NTSD is carried in SMB2_SET_INFO (SMB2_O_INFO_SECURITY) or an SMB2_CREATE SMB2_CREATE_SD_BUFFER context; set_info_sec()/ksmbd_vfs_set_sd_xattr() store that buffer, and a later SMB2_CREATE in smb2_open() loads it into smb_check_perm_dacl() from ksmbd_conn_handler_loop() on TCP/445.\nAC:L - The attacker sets pdacl-\u003esize smaller than the NTSD tail, inflates num_aces, and places an ACCESS_ALLOWED ACE after the declared DACL; smb_check_perm_dacl() then walks those bytes on the next SMB2_CREATE with no race or attacker-uncontrollable layout.\nPR:L - __handle_ksmbd_work() requires check_user_session()/get_ksmbd_tcon() before smb2_open()/smb2_set_info(); planting the NTSD needs FILE_WRITE_DAC/FILE_WRITE_OWNER in smb2_set_info_sec() or create rights for SMB2_CREATE_SD_BUFFER on an acl-xattr share, not a pre-auth path.\nUI:N - The attacker alone sends the SMB2_SET_INFO or SMB2_CREATE SD_BUFFER that stores the NTSD and the SMB2_CREATE that calls smb_check_perm_dacl(); no victim mount, open, or other interactive step is required.\nS:U - smb_check_perm_dacl() only mis-evaluates the stored DACL for ksmbd file opens; the resulting access grant stays inside the kernel SMB server and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - The SID-matching ACE walk in smb_check_perm_dacl() can select a post-pdacl-\u003esize ACCESS_ALLOWED ACE for the caller or Everyone and apply its access_req, so SMB2_CREATE is authorized for FILE_READ_DATA that the declared DACL would have denied with -EACCES.\nI:H - The same extra ACE supplies attacker-controlled ace-\u003eaccess_req; ACCESS_ALLOWED with FILE_WRITE_DATA/GENERIC_ALL makes smb_check_perm_dacl() accept a write SMB2_CREATE that parse_dacl() and smb_inherit_dacl() never grant from the bounded DACL.\nA:N - Both walks stay inside the NTSD (acl_size from pntsd_size); the bug only returns success instead of -EACCES and does not oops, panic, hang, or corrupt memory."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-18T17:53:28.059Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/a2051ffe452afad52f580b85a3fd8851933b1e7c"
        },
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        },
        {
          "url": "https://git.kernel.org/stable/c/79decd88dd3f0d42e7fb0689b1a7853bfa302459"
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      ],
      "title": "ksmbd: bound smb_check_perm_dacl() ACE walks by DACL size",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90153",
    "datePublished": "2026-09-17T16:06:46.296Z",
    "dateReserved": "2026-09-11T19:38:34.789Z",
    "dateUpdated": "2026-09-18T17:53:28.059Z",
    "state": "PUBLISHED"
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  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
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      "date": "2026-09-26",
      "epss": "0.00478",
      "percentile": "0.38756"
    },
    "nvd": {
      "cve": {
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                "product": "Linux",
                "programFiles": [
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        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: bound smb_check_perm_dacl() ACE walks by DACL size\n\nsmb_check_perm_dacl() validates that the DACL fits inside the NT\nsecurity descriptor, but then bounds its two ACE walks by the\nremaining NTSD length (acl_size) rather than the DACL\u0027s declared\nsize (pdacl_size).\n\nWhen pdacl-\u003esize is smaller than the trailing NTSD buffer, bytes\nafter the declared DACL boundary - still inside the stored security\ndescriptor - are parsed as ACEs during access checks.  A crafted\nDACL can place an access-granting ACE beyond pdacl-\u003esize, and the\ncurrent code accepts it during SMB2_CREATE access validation, while\nparse_dacl() and smb_inherit_dacl() stop at pdacl_size.\n\nBound both ACE walks by pdacl_size to match the DACL boundary\nsemantics used elsewhere in the server.\n\nValidation:\n- semantic KUnit harness shows the post-boundary ACE is selected\n  before the fix and rejected (EACCES) after it\n- linux master (7.2-rc6), x86_64"
          }
        ],
        "id": "CVE-2026-90153",
        "lastModified": "2026-09-18T18:17:44.427",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "NONE",
                "baseScore": 8.1,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N",
                "version": "3.1"
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              "impactScore": 5.2,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
            }
          ]
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        "published": "2026-09-17T17:17:08.370",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/79decd88dd3f0d42e7fb0689b1a7853bfa302459"
          },
          {
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            "url": "https://git.kernel.org/stable/c/8e4f75e979c1d9a51b0a48ac33d0cfd5f039ec67"
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          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/a2051ffe452afad52f580b85a3fd8851933b1e7c"
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          {
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            "url": "https://git.kernel.org/stable/c/a29f57a14c939586d84d7fd6a029bd1fd170098f"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/a4a307d149327dad5fb25187e1b03cebd1b04de6"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-21T16:32:09Z",
      "cve": "CVE-2026-90153",
      "id": "CVE-2026-90153",
      "initial_release_date": "2026-09-18T00:20:42Z",
      "product_status:known_affected": "96",
      "product_status:known_not_affected": "251",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-90153",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-90153.json",
      "version": "4"
    }
  }
}



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