smb: client: bound dirent name against end of SMB response in cifs_filldir

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-93787
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-24 17:17:11 UTC
Updated2026-09-25 05:17:02 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v3.1 8.1 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

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

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary8.1HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H
3.1CNADECLARED8.1HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 6e3b965267b7313903baba2739992b1e2e92d540 git Not specified
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 03003506c86f90312b0966283662c42fcab66e4b git Not specified
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 f8cf09a53a0dc1da298e9dd0ba5f21710cf119d6 git Not specified
CNA Linux Linux affected 6.12.111 semver Not specified
CNA Linux Linux affected 6.18.53 semver Not specified
CNA Linux Linux unaffected 6.12.111 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.53 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/f8cf09a53a0dc1da298e9dd0ba5f21710cf119d6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/6e3b965267b7313903baba2739992b1e2e92d540 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/03003506c86f90312b0966283662c42fcab66e4b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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