Vulnerability-Lookup

CNVD-2026-20424

Vulnerability from cnvd - Published: 2026-05-15

Title

Linux kernel smb_check_perm_dacl函数越界读取漏洞

Description

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在越界读取漏洞。该漏洞源于ksmbd的smb_check_perm_dacl()函数中ACE大小验证不足，攻击者可利用该漏洞导致越界读取。

Severity

高

Patch Name

Linux kernel smb_check_perm_dacl函数越界读取漏洞的补丁

Patch Description

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在越界读取漏洞。该漏洞源于ksmbd的smb_check_perm_dacl()函数中ACE大小验证不足，攻击者可利用该漏洞导致越界读取。目前，供应商发布了安全公告及相关补丁信息，修复了此漏洞。

Formal description

厂商已发布了漏洞修复程序，请及时关注更新： https://www.kernel.org/category/releases.html

Reference

https://nvd.nist.gov/vuln/detail/CVE-2026-31712

Impacted products

Name
['Linux Linux kernel >=6.13，<6.18.25', 'Linux Linux kernel >=6.19，<7.0.2', 'Linux Linux kernel >=5.15，<6.12.84']

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{
  "cves": {
    "cve": {
      "cveNumber": "CVE-2026-31712",
      "cveUrl": "https://nvd.nist.gov/vuln/detail/CVE-2026-31712"
    }
  },
  "description": "Linux kernel\u662f\u7f8e\u56fdLinux\u57fa\u91d1\u4f1a\u7684\u5f00\u6e90\u64cd\u4f5c\u7cfb\u7edfLinux\u6240\u4f7f\u7528\u7684\u5185\u6838\u3002\n\nLinux kernel\u5b58\u5728\u8d8a\u754c\u8bfb\u53d6\u6f0f\u6d1e\u3002\u8be5\u6f0f\u6d1e\u6e90\u4e8eksmbd\u7684smb_check_perm_dacl()\u51fd\u6570\u4e2dACE\u5927\u5c0f\u9a8c\u8bc1\u4e0d\u8db3\uff0c\u653b\u51fb\u8005\u53ef\u5229\u7528\u8be5\u6f0f\u6d1e\u5bfc\u81f4\u8d8a\u754c\u8bfb\u53d6\u3002",
  "formalWay": "\u5382\u5546\u5df2\u53d1\u5e03\u4e86\u6f0f\u6d1e\u4fee\u590d\u7a0b\u5e8f\uff0c\u8bf7\u53ca\u65f6\u5173\u6ce8\u66f4\u65b0\uff1a\r\nhttps://www.kernel.org/category/releases.html",
  "isEvent": "\u901a\u7528\u8f6f\u786c\u4ef6\u6f0f\u6d1e",
  "number": "CNVD-2026-20424",
  "openTime": "2026-05-15",
  "patchDescription": "Linux kernel\u662f\u7f8e\u56fdLinux\u57fa\u91d1\u4f1a\u7684\u5f00\u6e90\u64cd\u4f5c\u7cfb\u7edfLinux\u6240\u4f7f\u7528\u7684\u5185\u6838\u3002\r\n\r\nLinux kernel\u5b58\u5728\u8d8a\u754c\u8bfb\u53d6\u6f0f\u6d1e\u3002\u8be5\u6f0f\u6d1e\u6e90\u4e8eksmbd\u7684smb_check_perm_dacl()\u51fd\u6570\u4e2dACE\u5927\u5c0f\u9a8c\u8bc1\u4e0d\u8db3\uff0c\u653b\u51fb\u8005\u53ef\u5229\u7528\u8be5\u6f0f\u6d1e\u5bfc\u81f4\u8d8a\u754c\u8bfb\u53d6\u3002\u76ee\u524d\uff0c\u4f9b\u5e94\u5546\u53d1\u5e03\u4e86\u5b89\u5168\u516c\u544a\u53ca\u76f8\u5173\u8865\u4e01\u4fe1\u606f\uff0c\u4fee\u590d\u4e86\u6b64\u6f0f\u6d1e\u3002",
  "patchName": "Linux kernel smb_check_perm_dacl\u51fd\u6570\u8d8a\u754c\u8bfb\u53d6\u6f0f\u6d1e\u7684\u8865\u4e01",
  "products": {
    "product": [
      "Linux Linux kernel \u003e=6.13\uff0c\u003c6.18.25",
      "Linux Linux kernel \u003e=6.19\uff0c\u003c7.0.2",
      "Linux Linux kernel \u003e=5.15\uff0c\u003c6.12.84"
    ]
  },
  "referenceLink": "https://nvd.nist.gov/vuln/detail/CVE-2026-31712",
  "serverity": "\u9ad8",
  "submitTime": "2026-05-11",
  "title": "Linux kernel smb_check_perm_dacl\u51fd\u6570\u8d8a\u754c\u8bfb\u53d6\u6f0f\u6d1e"
}

CVE-2026-31712 (GCVE-0-2026-31712)

Vulnerability from cvelistv5 – Published: 2026-05-01 13:56 – Updated: 2026-08-05 12:24

Title

ksmbd: require minimum ACE size in smb_check_perm_dacl()

Summary

In the Linux kernel, the following vulnerability has been resolved: ksmbd: require minimum ACE size in smb_check_perm_dacl() Both ACE-walk loops in smb_check_perm_dacl() only guard against an under-sized remaining buffer, not against an ACE whose declared `ace->size` is smaller than the struct it claims to describe: if (offsetof(struct smb_ace, access_req) > aces_size) break; ace_size = le16_to_cpu(ace->size); if (ace_size > aces_size) break; The first check only requires the 4-byte ACE header to be in bounds; it does not require access_req (4 bytes at offset 4) to be readable. An attacker who has set a crafted DACL on a file they own can declare ace->size == 4 with aces_size == 4, pass both checks, and then granted |= le32_to_cpu(ace->access_req); /* upper loop */ compare_sids(&sid, &ace->sid); /* lower loop */ reads access_req at offset 4 (OOB by up to 4 bytes) and ace->sid at offset 8 (OOB by up to CIFS_SID_BASE_SIZE + SID_MAX_SUB_AUTHORITIES * 4 bytes). Tighten both loops to require ace_size >= offsetof(struct smb_ace, sid) + CIFS_SID_BASE_SIZE which is the smallest valid on-wire ACE layout (4-byte header + 4-byte access_req + 8-byte sid base with zero sub-auths). Also reject ACEs whose sid.num_subauth exceeds SID_MAX_SUB_AUTHORITIES before letting compare_sids() dereference sub_auth[] entries. parse_sec_desc() already enforces an equivalent check (lines 441-448); smb_check_perm_dacl() simply grew weaker validation over time. Reachability: authenticated SMB client with permission to set an ACL on a file. On a subsequent CREATE against that file, the kernel walks the stored DACL via smb_check_perm_dacl() and triggers the OOB read. Not pre-auth, and the OOB read is not reflected to the attacker, but KASAN reports and kernel state corruption are possible.

Severity

8.3 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H

Assigner

Linux mitre root

References

7 references

URL	Tags
https://git.kernel.org/stable/c/282cbbb476b9f3579…
https://git.kernel.org/stable/c/f20adc4ef7428bc48…
https://git.kernel.org/stable/c/325d4ac11f526cb89…
https://git.kernel.org/stable/c/95e5aa3c3261da8c9…
https://git.kernel.org/stable/c/90089584b2e25c451…
https://git.kernel.org/stable/c/151b1799861fde380…
https://git.kernel.org/stable/c/d07b26f39246a8239…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 282cbbb476b9f35793452bc461934af4c7eca169 (git) Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < f20adc4ef7428bc485ee83fd1a592252fb87718b (git) Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 325d4ac11f526cb8964cff14548ccf02d8c756d8 (git) Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 95e5aa3c3261da8c95b27d7aecf8ee39b9f86a4c (git) Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 90089584b2e25c4510b7b987387b4405f0673ece (git) Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 151b1799861fde38087c08f613abc2843ef597b0 (git) Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < d07b26f39246a82399661936dd0c853983cfade7 (git)
Linux	Linux	Affected: 5.15 Unaffected: 0 , < 5.15 (semver) Unaffected: 5.15.210 , ≤ 5.15.* (semver) Unaffected: 6.1.176 , ≤ 6.1.* (semver) Unaffected: 6.6.140 , ≤ 6.6.* (semver) Unaffected: 6.12.84 , ≤ 6.12.* (semver) Unaffected: 6.18.25 , ≤ 6.18.* (semver) Unaffected: 7.0.2 , ≤ 7.0.* (semver) Unaffected: 7.1 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/smbacl.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "282cbbb476b9f35793452bc461934af4c7eca169",
              "status": "affected",
              "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
              "versionType": "git"
            },
            {
              "lessThan": "f20adc4ef7428bc485ee83fd1a592252fb87718b",
              "status": "affected",
              "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
              "versionType": "git"
            },
            {
              "lessThan": "325d4ac11f526cb8964cff14548ccf02d8c756d8",
              "status": "affected",
              "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
              "versionType": "git"
            },
            {
              "lessThan": "95e5aa3c3261da8c95b27d7aecf8ee39b9f86a4c",
              "status": "affected",
              "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
              "versionType": "git"
            },
            {
              "lessThan": "90089584b2e25c4510b7b987387b4405f0673ece",
              "status": "affected",
              "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
              "versionType": "git"
            },
            {
              "lessThan": "151b1799861fde38087c08f613abc2843ef597b0",
              "status": "affected",
              "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
              "versionType": "git"
            },
            {
              "lessThan": "d07b26f39246a82399661936dd0c853983cfade7",
              "status": "affected",
              "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/smbacl.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.15"
            },
            {
              "lessThan": "5.15",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.210",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.176",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.140",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.84",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.25",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.2",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.210",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.176",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.140",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.84",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.25",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.0.2",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: require minimum ACE size in smb_check_perm_dacl()\n\nBoth ACE-walk loops in smb_check_perm_dacl() only guard against an\nunder-sized remaining buffer, not against an ACE whose declared\n`ace-\u003esize` is smaller than the struct it claims to describe:\n\n  if (offsetof(struct smb_ace, access_req) \u003e aces_size)\n      break;\n  ace_size = le16_to_cpu(ace-\u003esize);\n  if (ace_size \u003e aces_size)\n      break;\n\nThe first check only requires the 4-byte ACE header to be in bounds;\nit does not require access_req (4 bytes at offset 4) to be readable.\nAn attacker who has set a crafted DACL on a file they own can declare\nace-\u003esize == 4 with aces_size == 4, pass both checks, and then\n\n  granted |= le32_to_cpu(ace-\u003eaccess_req);               /* upper loop */\n  compare_sids(\u0026sid, \u0026ace-\u003esid);                         /* lower loop */\n\nreads access_req at offset 4 (OOB by up to 4 bytes) and ace-\u003esid at\noffset 8 (OOB by up to CIFS_SID_BASE_SIZE + SID_MAX_SUB_AUTHORITIES\n* 4 bytes).\n\nTighten both loops to require\n\n  ace_size \u003e= offsetof(struct smb_ace, sid) + CIFS_SID_BASE_SIZE\n\nwhich is the smallest valid on-wire ACE layout (4-byte header +\n4-byte access_req + 8-byte sid base with zero sub-auths).  Also\nreject ACEs whose sid.num_subauth exceeds SID_MAX_SUB_AUTHORITIES\nbefore letting compare_sids() dereference sub_auth[] entries.\n\nparse_sec_desc() already enforces an equivalent check (lines 441-448);\nsmb_check_perm_dacl() simply grew weaker validation over time.\n\nReachability: authenticated SMB client with permission to set an ACL\non a file.  On a subsequent CREATE against that file, the kernel\nwalks the stored DACL via smb_check_perm_dacl() and triggers the\nOOB read.  Not pre-auth, and the OOB read is not reflected to the\nattacker, but KASAN reports and kernel state corruption are\npossible."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.3,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - ksmbd is an in-kernel SMB server reachable over the network via SMB2/SMB3 requests, typically TCP/445. The vulnerable DACL walk is reached from remote SMB CREATE processing after a crafted stored ACL is present.\nAC:L - No race or uncontrollable timing is required; an attacker can set a malformed DACL and then trigger a subsequent CREATE against that file. ACL xattr support is a reasonable ksmbd deployment configuration, not an exploit-complexity barrier.\nPR:L - The path is not pre-authentication: SMB2 commands require a valid authenticated session and tree connect. The attacker needs ordinary SMB credentials with permission to set an ACL on a file they control, not kernel/root privileges.\nUI:N - After authentication, the attacker can send the ACL-setting and CREATE requests directly. No victim user action is required.\nS:U - The impact remains within the kernel/ksmbd host security authority. There is no VM, IOMMU, or sandbox boundary crossing.\nC:H - The bug causes attacker-triggered out-of-bounds reads from kernel heap data beyond the stored security descriptor, including SID fields. Although not directly reflected, this is more than a strictly bounded few-byte read and the higher-severity rule makes High appropriate.\nI:L - The out-of-bounds data is consumed as permission-check state such as ACE access bits, so it can corrupt ksmbd access-control decisions for the requested object. There is no clear arbitrary kernel write or control-flow hijack primitive, so the integrity impact is limited rather than High.\nA:H - The malformed ACE can reliably trigger kernel out-of-bounds reads during SMB CREATE, producing KASAN reports and possible kernel oops/panic depending on configuration. A remote authenticated user can repeat the trigger for denial of service."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:24:46.463Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/282cbbb476b9f35793452bc461934af4c7eca169"
        },
        {
          "url": "https://git.kernel.org/stable/c/f20adc4ef7428bc485ee83fd1a592252fb87718b"
        },
        {
          "url": "https://git.kernel.org/stable/c/325d4ac11f526cb8964cff14548ccf02d8c756d8"
        },
        {
          "url": "https://git.kernel.org/stable/c/95e5aa3c3261da8c95b27d7aecf8ee39b9f86a4c"
        },
        {
          "url": "https://git.kernel.org/stable/c/90089584b2e25c4510b7b987387b4405f0673ece"
        },
        {
          "url": "https://git.kernel.org/stable/c/151b1799861fde38087c08f613abc2843ef597b0"
        },
        {
          "url": "https://git.kernel.org/stable/c/d07b26f39246a82399661936dd0c853983cfade7"
        }
      ],
      "title": "ksmbd: require minimum ACE size in smb_check_perm_dacl()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31712",
    "datePublished": "2026-05-01T13:56:08.583Z",
    "dateReserved": "2026-03-09T15:48:24.133Z",
    "dateUpdated": "2026-08-05T12:24:46.463Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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CNVD-2026-20424

CVE-2026-31712 (GCVE-0-2026-31712)

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Nomenclature

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