FKIE_CVE-2026-68099

Vulnerability from fkie_nvd - Published: 2026-08-10 13:19 - Updated: 2026-08-17 05:18
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: restore DACL size on check_add_overflow() to avoid malformed ACL check_add_overflow() unconditionally writes the truncated sum into *d even on overflow, per its contract in include/linux/overflow.h. The four check_add_overflow() guards in set_posix_acl_entries_dacl() and set_ntacl_dacl() break out of the ACE-building loops on overflow, but the truncated *size is then consumed downstream at the end of set_ntacl_dacl(): pndacl->size = cpu_to_le16(le16_to_cpu(pndacl->size) + size); This produces an on-wire NT ACL whose pndacl->size under-reports the bytes actually written by the preceding fill_ace_for_sid()/memcpy() calls, yielding a malformed ACL that can trigger out-of-bounds reads when re-parsed by clients or ksmbd itself. Restore *size to its pre-addition value on each overflow branch (via `*size -= ace_sz` / `size -= nt_ace_size`) so that after the break, *size once again holds the cumulative size of the successfully-written ACEs. The committed ACL is then truncated-but-self-consistent rather than malformed. The ksmbd DACL builders are the only check_add_overflow() sites found where an overflow path breaks out of a loop and the destination value is consumed afterward. The other nearby break-style cases either return -EINVAL on overflow (transport_ipc.c) or break without consuming the overflowed destination value afterward (buildid.c).
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/0bf38372821b1526f31538a7d9811844c55c7f38
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/847ecd4eb3c117c3d2f13f1e7ab506543aad8183
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/bbf0a8e931204ecdab494a88d43b0a24a04285c5
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/bc90144ce8bb7fcf05ad9417c7adb4e9509d9e13
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f4fcd0c1a243d449307b887fafee23921e9db5ab
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "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": "f4fcd0c1a243d449307b887fafee23921e9db5ab",
              "status": "affected",
              "version": "8d5729350b236896f51379588d9a690b7fafb8db",
              "versionType": "git"
            },
            {
              "lessThan": "0bf38372821b1526f31538a7d9811844c55c7f38",
              "status": "affected",
              "version": "e1955a94b6f17f4b058afa955a6f187eb3ed7615",
              "versionType": "git"
            },
            {
              "lessThan": "847ecd4eb3c117c3d2f13f1e7ab506543aad8183",
              "status": "affected",
              "version": "5e7b8f3c539d69b2ed5f2408e2f75e68ce7eef43",
              "versionType": "git"
            },
            {
              "lessThan": "bc90144ce8bb7fcf05ad9417c7adb4e9509d9e13",
              "status": "affected",
              "version": "299f962c0b02d048fb45d248b4da493d03f3175d",
              "versionType": "git"
            },
            {
              "lessThan": "bbf0a8e931204ecdab494a88d43b0a24a04285c5",
              "status": "affected",
              "version": "299f962c0b02d048fb45d248b4da493d03f3175d",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "41e53a773db6342ac9a689ee5ba635c31744c9f0",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "ef7902be3f215b6bf7babe4dc9dd9a7d57dad7a7",
              "versionType": "git"
            },
            {
              "lessThan": "6.6.148",
              "status": "affected",
              "version": "6.6.136",
              "versionType": "semver"
            },
            {
              "lessThan": "6.12.101",
              "status": "affected",
              "version": "6.12.84",
              "versionType": "semver"
            },
            {
              "lessThan": "6.18.42",
              "status": "affected",
              "version": "6.18.25",
              "versionType": "semver"
            },
            {
              "lessThan": "6.2",
              "status": "affected",
              "version": "6.1.175",
              "versionType": "semver"
            },
            {
              "lessThan": "7.1",
              "status": "affected",
              "version": "7.0.2",
              "versionType": "semver"
            }
          ]
        },
        {
          "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": "7.1"
            },
            {
              "lessThan": "7.1",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.148",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.101",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.42",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: restore DACL size on check_add_overflow() to avoid malformed ACL\n\ncheck_add_overflow() unconditionally writes the truncated sum into *d\neven on overflow, per its contract in include/linux/overflow.h.\nThe four check_add_overflow() guards in set_posix_acl_entries_dacl()\nand set_ntacl_dacl() break out of the ACE-building loops on overflow,\nbut the truncated *size is then consumed downstream at the end of\nset_ntacl_dacl():\n\n    pndacl-\u003esize = cpu_to_le16(le16_to_cpu(pndacl-\u003esize) + size);\n\nThis produces an on-wire NT ACL whose pndacl-\u003esize under-reports the\nbytes actually written by the preceding fill_ace_for_sid()/memcpy()\ncalls, yielding a malformed ACL that can trigger out-of-bounds reads\nwhen re-parsed by clients or ksmbd itself.\n\nRestore *size to its pre-addition value on each overflow branch (via\n`*size -= ace_sz` / `size -= nt_ace_size`) so that after the break,\n*size once again holds the cumulative size of the successfully-written\nACEs. The committed ACL is then truncated-but-self-consistent rather\nthan malformed.\n\nThe ksmbd DACL builders are the only check_add_overflow() sites found\nwhere an overflow path breaks out of a loop and the destination value\nis consumed afterward. The other nearby break-style cases either\nreturn -EINVAL on overflow (transport_ipc.c) or break without\nconsuming the overflowed destination value afterward (buildid.c)."
    }
  ],
  "id": "CVE-2026-68099",
  "lastModified": "2026-08-17T05:18:09.283",
  "metrics": {},
  "published": "2026-08-10T13:19:54.350",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/0bf38372821b1526f31538a7d9811844c55c7f38"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/847ecd4eb3c117c3d2f13f1e7ab506543aad8183"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/bbf0a8e931204ecdab494a88d43b0a24a04285c5"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/bc90144ce8bb7fcf05ad9417c7adb4e9509d9e13"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/f4fcd0c1a243d449307b887fafee23921e9db5ab"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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