GHSA-5JGF-2W89-7334

Vulnerability from github – Published: 2026-05-01 15:30 – Updated: 2026-05-03 09:33
VLAI?
Details

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

ksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment

smb2_get_ea() applies 4-byte alignment padding via memset() after writing each EA entry. The bounds check on buf_free_len is performed before the value memcpy, but the alignment memset fires unconditionally afterward with no check on remaining space.

When the EA value exactly fills the remaining buffer (buf_free_len == 0 after value subtraction), the alignment memset writes 1-3 NUL bytes past the buf_free_len boundary. In compound requests where the response buffer is shared across commands, the first command (e.g., READ) can consume most of the buffer, leaving a tight remainder for the QUERY_INFO EA response. The alignment memset then overwrites past the physical kvmalloc allocation into adjacent kernel heap memory.

Add a bounds check before the alignment memset to ensure buf_free_len can accommodate the padding bytes.

This is the same bug pattern fixed by commit beef2634f81f ("ksmbd: fix potencial OOB in get_file_all_info() for compound requests") and commit fda9522ed6af ("ksmbd: fix OOB write in QUERY_INFO for compound requests"), both of which added bounds checks before unconditional writes in QUERY_INFO response handlers.

Severity ?
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2026-31705"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-05-01T14:16:20Z",
    "severity": "CRITICAL"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment\n\nsmb2_get_ea() applies 4-byte alignment padding via memset() after\nwriting each EA entry. The bounds check on buf_free_len is performed\nbefore the value memcpy, but the alignment memset fires unconditionally\nafterward with no check on remaining space.\n\nWhen the EA value exactly fills the remaining buffer (buf_free_len == 0\nafter value subtraction), the alignment memset writes 1-3 NUL bytes\npast the buf_free_len boundary. In compound requests where the response\nbuffer is shared across commands, the first command (e.g., READ) can\nconsume most of the buffer, leaving a tight remainder for the QUERY_INFO\nEA response. The alignment memset then overwrites past the physical\nkvmalloc allocation into adjacent kernel heap memory.\n\nAdd a bounds check before the alignment memset to ensure buf_free_len\ncan accommodate the padding bytes.\n\nThis is the same bug pattern fixed by commit beef2634f81f (\"ksmbd: fix\npotencial OOB in get_file_all_info() for compound requests\") and\ncommit fda9522ed6af (\"ksmbd: fix OOB write in QUERY_INFO for compound\nrequests\"), both of which added bounds checks before unconditional\nwrites in QUERY_INFO response handlers.",
  "id": "GHSA-5jgf-2w89-7334",
  "modified": "2026-05-03T09:33:09Z",
  "published": "2026-05-01T15:30:33Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31705"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/30010c952077a1c89ecdd71fc4d574c75a8f5617"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/790304c02bf9bd7b8171feda4294d6e62d32ae8f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/922d48fe8c19f388ffa2f709f33acaae4e408de2"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/98f3de6ef4efbd899348d333f0902dc4ff14380c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ffbce350c6fd1e99116ea57383b9031717e36d3b"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}


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