Vulnerability-Lookup

GHSA-XRHM-HWVC-W6Q3

Vulnerability from github – Published: 2026-08-15 06:32 – Updated: 2026-08-17 06:33

Details

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: reject undersized DACLs before parsing ACEs

parse_dacl() limits the attacker-controlled ACE count by comparing it with the number of minimal ACEs that fit in the DACL size. The DACL size field is 16 bits, but the expression subtracts sizeof(struct smb_acl). Because sizeof() is unsigned, a DACL size smaller than the ACL header underflows to a large size_t.

A malicious client can reach this with:

SMB2_SET_INFO (InfoType=SMB2_O_INFO_SECURITY) -> smb2_set_info_sec() -> set_info_sec() -> parse_sec_desc() -> parse_dacl() -> init_acl_state(..., 0xffff) -> init_acl_state(..., 0xffff) -> kmalloc_objs(..., 0xffff)

Thus a malformed security descriptor can make num_aces pass the guard and drive large temporary ACL state and pointer-array allocations.

Reject DACLs smaller than struct smb_acl before doing the subtraction, so the ACE count check cannot be bypassed by the underflow.

Severity

8.8 (High)


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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-72382"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-15T06:22:11Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: reject undersized DACLs before parsing ACEs\n\nparse_dacl() limits the attacker-controlled ACE count by comparing it\nwith the number of minimal ACEs that fit in the DACL size. The DACL size\nfield is 16 bits, but the expression subtracts sizeof(struct smb_acl).\nBecause sizeof() is unsigned, a DACL size smaller than the ACL header\nunderflows to a large size_t.\n\nA malicious client can reach this with:\n\nSMB2_SET_INFO (InfoType=SMB2_O_INFO_SECURITY)\n  -\u003e smb2_set_info_sec()\n  -\u003e set_info_sec()\n  -\u003e parse_sec_desc()\n  -\u003e parse_dacl()\n     -\u003e init_acl_state(..., 0xffff)\n     -\u003e init_acl_state(..., 0xffff)\n     -\u003e kmalloc_objs(..., 0xffff)\n\nThus a malformed security descriptor can make num_aces pass the guard\nand drive large temporary ACL state and pointer-array allocations.\n\nReject DACLs smaller than struct smb_acl before doing the subtraction,\nso the ACE count check cannot be bypassed by the underflow.",
  "id": "GHSA-xrhm-hwvc-w6q3",
  "modified": "2026-08-17T06:33:26Z",
  "published": "2026-08-15T06:32:22Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-72382"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/15a9e9b8f7f5d7f380ae54c6f5bcbc0bdcb0f3cd"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/16fb65ec15fe7c90f50a2115854bfd9a032d4023"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/282847c0cf22f2e961155ac8e42f6eeab7e16049"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/60908f7ebcd9b6cde74ad5711fab0f49c7970949"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d020e7f27bf65eecd3805404702f716b2b6d9e73"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-72382 (GCVE-0-2026-72382)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:56 – Updated: 2026-08-17 05:43

Title

ksmbd: reject undersized DACLs before parsing ACEs

Summary

In the Linux kernel, the following vulnerability has been resolved: ksmbd: reject undersized DACLs before parsing ACEs parse_dacl() limits the attacker-controlled ACE count by comparing it with the number of minimal ACEs that fit in the DACL size. The DACL size field is 16 bits, but the expression subtracts sizeof(struct smb_acl). Because sizeof() is unsigned, a DACL size smaller than the ACL header underflows to a large size_t. A malicious client can reach this with: SMB2_SET_INFO (InfoType=SMB2_O_INFO_SECURITY) -> smb2_set_info_sec() -> set_info_sec() -> parse_sec_desc() -> parse_dacl() -> init_acl_state(..., 0xffff) -> init_acl_state(..., 0xffff) -> kmalloc_objs(..., 0xffff) Thus a malformed security descriptor can make num_aces pass the guard and drive large temporary ACL state and pointer-array allocations. Reject DACLs smaller than struct smb_acl before doing the subtraction, so the ACE count check cannot be bypassed by the underflow.

Severity

8.8 (High)


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

Assigner

Linux CNA under the mitre root

CNA scorecard D 53/100 over 6992 records in the last 180 days details

References

5 references

URL	Tags
https://git.kernel.org/stable/c/16fb65ec15fe7c90f…
https://git.kernel.org/stable/c/282847c0cf22f2e96…
https://git.kernel.org/stable/c/d020e7f27bf65eecd…
https://git.kernel.org/stable/c/15a9e9b8f7f5d7f38…
https://git.kernel.org/stable/c/60908f7ebcd9b6cde…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 16fb65ec15fe7c90f50a2115854bfd9a032d4023 (git) Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 282847c0cf22f2e961155ac8e42f6eeab7e16049 (git) Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < d020e7f27bf65eecd3805404702f716b2b6d9e73 (git) Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 15a9e9b8f7f5d7f380ae54c6f5bcbc0bdcb0f3cd (git) Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 60908f7ebcd9b6cde74ad5711fab0f49c7970949 (git)
Linux	Linux	Affected: 5.15 Unaffected: 0 , < 5.15 (semver) Unaffected: 6.6.145 , ≤ 6.6.* (semver) Unaffected: 6.12.97 , ≤ 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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{
  "containers": {
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      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/smbacl.c"
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              "versionType": "semver"
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              "status": "unaffected",
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              "version": "7.1.5",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
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        }
      ],
      "cpeApplicability": [
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              "cpeMatch": [
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: reject undersized DACLs before parsing ACEs\n\nparse_dacl() limits the attacker-controlled ACE count by comparing it\nwith the number of minimal ACEs that fit in the DACL size. The DACL size\nfield is 16 bits, but the expression subtracts sizeof(struct smb_acl).\nBecause sizeof() is unsigned, a DACL size smaller than the ACL header\nunderflows to a large size_t.\n\nA malicious client can reach this with:\n\nSMB2_SET_INFO (InfoType=SMB2_O_INFO_SECURITY)\n  -\u003e smb2_set_info_sec()\n  -\u003e set_info_sec()\n  -\u003e parse_sec_desc()\n  -\u003e parse_dacl()\n     -\u003e init_acl_state(..., 0xffff)\n     -\u003e init_acl_state(..., 0xffff)\n     -\u003e kmalloc_objs(..., 0xffff)\n\nThus a malformed security descriptor can make num_aces pass the guard\nand drive large temporary ACL state and pointer-array allocations.\n\nReject DACLs smaller than struct smb_acl before doing the subtraction,\nso the ACE count check cannot be bypassed by the underflow."
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          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The flaw is reached through ksmbd\u0027s in-kernel SMB2 server on TCP/445 via SMB2_SET_INFO (InfoType=SMB2_O_INFO_SECURITY) or SMB2 CREATE with an SD buffer, both handled from remote network input.\nAC:L - An attacker reliably triggers the bug by sending a crafted security descriptor with DACL size below 8 bytes and a large num_aces (e.g. 0xFFFF), bypassing the underflowed ACE-count check without special timing or victim state.\nPR:L - Exploitation requires an authenticated SMB session, a writable tree connect, an open file handle (or CREATE with SD buffer), and FILE_WRITE_DAC or FILE_WRITE_OWNER access on that object.\nUI:N - No victim interaction is required beyond the attacker sending malicious SMB2 protocol requests to an exposed ksmbd server.\nS:U - Impact is confined to kernel memory exhaustion and ksmbd availability within the same host security authority; it does not cross VM, container, or IOMMU boundaries.\nC:H - The unsigned underflow bypasses DACL bounds validation, letting attacker-controlled num_aces drive multi-megabyte kernel heap allocations and parse attacker-supplied ACE data from malformed security descriptors.\nI:H - Attacker-controlled allocation sizing from bypassed validation creates large heap manipulation primitives in kernel context, consistent with similar ksmbd DACL integer-validation flaws scored at high integrity impact.\nA:H - Each malicious request forces roughly 2.5 MB of kernel allocations; repeated or concurrent SMB2_SET_INFO calls can exhaust memory, trigger OOM/page-allocator failures, and deny service to ksmbd and the host."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T05:43:33.111Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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        {
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      "title": "ksmbd: reject undersized DACLs before parsing ACEs",
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    "cveId": "CVE-2026-72382",
    "datePublished": "2026-08-15T05:56:14.103Z",
    "dateReserved": "2026-08-09T03:40:39.923Z",
    "dateUpdated": "2026-08-17T05:43:33.111Z",
    "state": "PUBLISHED"
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}

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.

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