GHSA-Q6FC-4C58-35PF

Vulnerability from github – Published: 2026-07-19 18:31 – Updated: 2026-07-20 15:31
VLAI
Details

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

fs/statmount: fix slab out-of-bounds write in statmount_mnt_idmap

statmount_mnt_idmap() writes one mapping with seq_printf() and then manually advances seq->count to include the NUL separator.

If seq_printf() overflows, seq_set_overflow() sets seq->count to seq->size. The manual seq->count++ changes this to seq->size + 1. seq_has_overflowed() then no longer detects the overflow. The corrupted count returns to statmount_string(), which later executes:

seq->buf[seq->count++] = '\0';

This causes a 1-byte NULL out-of-bounds write on the dynamically allocated seq buffer.

Fix this by checking for overflow immediately after seq_printf().

Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2026-64074"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-19T16:17:48Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nfs/statmount: fix slab out-of-bounds write in statmount_mnt_idmap\n\nstatmount_mnt_idmap() writes one mapping with seq_printf() and then\nmanually advances seq-\u003ecount to include the NUL separator.\n\nIf seq_printf() overflows, seq_set_overflow() sets seq-\u003ecount to\nseq-\u003esize. The manual seq-\u003ecount++ changes this to seq-\u003esize + 1.\nseq_has_overflowed() then no longer detects the overflow. The corrupted\ncount returns to statmount_string(), which later executes:\n\n    seq-\u003ebuf[seq-\u003ecount++] = \u0027\\0\u0027;\n\nThis causes a 1-byte NULL out-of-bounds write on the dynamically\nallocated seq buffer.\n\nFix this by checking for overflow immediately after seq_printf().",
  "id": "GHSA-q6fc-4c58-35pf",
  "modified": "2026-07-20T15:31:58Z",
  "published": "2026-07-19T18:31:51Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64074"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/93614949dc86f068e3c32c32cf1ee2a2323177a7"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a3bf0f28d4ba16e1f35f8c983bb04426b87e2a78"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e37ea2c6f17f273813ea4e8e94c102591d598ce1"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}



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