GHSA-59GW-X2M7-5P58
Vulnerability from github – Published: 2026-09-24 18:31 – Updated: 2026-09-25 06:30In the Linux kernel, the following vulnerability has been resolved:
smb: client: bound dirent name against end of SMB response in cifs_filldir
cifs_filldir() copies the entry name out of an SMB1 TRANS2_FIND_FIRST / FIND_NEXT response using a length (de.namelen) supplied by the server. The kmalloc'd SMB response buffer is bounded, but nothing checks that de.name + de.namelen still lies inside that buffer before the eventual filldir64() -> verify_dirent_name() -> memchr() reads namelen bytes.
A hostile SMB1 server that returns an oversized FileNameLength in a directory entry therefore causes memchr() to read past the end of the response slab buffer. Reachable from any user who can list a directory on a CIFS mount served by an attacker-controlled server (getdents64() on the mounted directory):
BUG: KASAN: slab-out-of-bounds in memchr+0x71/0x80 Read of size 1 at addr ffff88800e0640cc by task poc/115 Call Trace: dump_stack_lvl+0x64/0x80 print_report+0xce/0x620 kasan_report+0xec/0x120 memchr+0x71/0x80 filldir64+0x4c/0x6a0 cifs_filldir.constprop.0+0x9bb/0x1e00 cifs_readdir+0x2101/0x3380 iterate_dir+0x19c/0x520 __x64_sys_getdents64+0x126/0x210 do_syscall_64+0x107/0x5a0 entry_SYSCALL_64_after_hwframe+0x77/0x7f
Pass the end-of-response pointer down to cifs_filldir() and reject entries whose name would extend past that boundary.
This bug was discovered by Artiphishell's vTriage pipeline, which generated a userspace reproducer (an emulated hostile SMB1 server plus a getdents64() client) that reliably triggers the KASAN report on an unpatched kernel. The fix below was drafted with the Claude coding assistant; a userspace reproducer is available on request.
{
"affected": [],
"aliases": [
"CVE-2026-93787"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-24T17:17:11Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: bound dirent name against end of SMB response in cifs_filldir\n\ncifs_filldir() copies the entry name out of an SMB1 TRANS2_FIND_FIRST /\nFIND_NEXT response using a length (de.namelen) supplied by the server.\nThe kmalloc\u0027d SMB response buffer is bounded, but nothing checks that\nde.name + de.namelen still lies inside that buffer before the eventual\nfilldir64() -\u003e verify_dirent_name() -\u003e memchr() reads namelen bytes.\n\nA hostile SMB1 server that returns an oversized FileNameLength in a\ndirectory entry therefore causes memchr() to read past the end of the\nresponse slab buffer. Reachable from any user who can list a directory\non a CIFS mount served by an attacker-controlled server (getdents64()\non the mounted directory):\n\n BUG: KASAN: slab-out-of-bounds in memchr+0x71/0x80\n Read of size 1 at addr ffff88800e0640cc by task poc/115\n Call Trace:\n dump_stack_lvl+0x64/0x80\n print_report+0xce/0x620\n kasan_report+0xec/0x120\n memchr+0x71/0x80\n filldir64+0x4c/0x6a0\n cifs_filldir.constprop.0+0x9bb/0x1e00\n cifs_readdir+0x2101/0x3380\n iterate_dir+0x19c/0x520\n __x64_sys_getdents64+0x126/0x210\n do_syscall_64+0x107/0x5a0\n entry_SYSCALL_64_after_hwframe+0x77/0x7f\n\nPass the end-of-response pointer down to cifs_filldir() and reject\nentries whose name would extend past that boundary.\n\nThis bug was discovered by Artiphishell\u0027s vTriage pipeline, which\ngenerated a userspace reproducer (an emulated hostile SMB1 server plus\na getdents64() client) that reliably triggers the KASAN report on an\nunpatched kernel. The fix below was drafted with the Claude coding\nassistant; a userspace reproducer is available on request.",
"id": "GHSA-59gw-x2m7-5p58",
"modified": "2026-09-25T06:30:29Z",
"published": "2026-09-24T18:31:28Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-93787"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/03003506c86f90312b0966283662c42fcab66e4b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6e3b965267b7313903baba2739992b1e2e92d540"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f8cf09a53a0dc1da298e9dd0ba5f21710cf119d6"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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