CVE-2026-93787
HighCVSS 8.1Exploitation Probability (EPSS)
Low risk24th percentile - higher than 24% of all known CVEs
Summary
In the Linux kernel CIFS (SMB1) module, cifs_filldir() copies directory entry names from an SMB response using a server-supplied length without checking that the name stays within the response buffer. A malicious SMB1 server returning an oversized FileNameLength causes memchr() to read past the end of the slab buffer.
Risk Assessment
An attacker controlling an SMB1 server can trigger a KASAN slab-out-of-bounds read when a local user lists a directory on a CIFS mount, potentially causing a kernel crash or memory corruption. This could lead to denial of service or privilege escalation.
Recommendation
Apply the latest Linux kernel patch for CVE-2026-93787, which passes the end-of-response pointer to cifs_filldir() and rejects out-of-bounds entries. Restrict access to untrusted SMB1 servers or disable SMB1 if not needed.
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Original NVD description (English source)
In 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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS