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smb: client: fix off-by-8 bounds check in check_wsl_eas()

Type: advisorySources: OSV

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix off-by-8 bounds check in check_wsl_eas() The bounds check uses (u8 *)ea + nlen + 1 + vlen as the end of the EA name and value, but ea_data sits at offset sizeof(struct smb2_file_full_ea_info) = 8 from ea, not at offset 0. The strncmp() later reads ea->ea_data[0..nlen-1] and the value bytes follow at ea_data[nlen+1..nlen+vlen], so the actual end is ea->ea_data + nlen + 1 + vlen. Isn't pointer math fun? The earlier check (u8 *)ea > end - sizeof(*ea) only guarantees the 8-byte header is in bounds, but since the last EA is placed within 8 bytes of the end of the response, the name and value bytes are read past the end of iov. Fix this mess all up by using ea->ea_data as the base for the bounds check. An "untrusted" server can use this to leak up to 8 bytes of kernel heap into the EA name comparison and influence which WSL xattr the data is interpreted as.

Products
Kernel
Affected versions
Not specified
Fixed versions
6.12.83, 6.18.24, 6.19.14, 6.6.136, 7.0.1
CVEs
CVE-2026-31614
Confirmed fixed CVEs
Not specified
Updated in this feed
4 Nov 2026, 16:19 UTC · Revision 1

Source evidence

smb: client: fix off-by-8 bounds check in check_wsl_eas()

core-osv · Original source

Published 24 Apr 2026, 14:42 UTC

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix off-by-8 bounds check in check_wsl_eas() The bounds check uses (u8 *)ea + nlen + 1 + vlen as the end of the EA name and value, but ea_data sits at offset sizeof(struct smb2_file_full_ea_info) = 8 from ea, not at offset 0. The strncmp() later reads ea->ea_data[0..nlen-1] and the value bytes follow at ea_data[nlen+1..nlen+vlen], so the actual end is ea->ea_data + nlen + 1 + vlen. Isn't pointer math fun? The earlier check (u8 *)ea > end - sizeof(*ea) only guarantees the 8-byte header is in bounds, but since the last EA is placed within 8 bytes of the end of the response, the name and value bytes are read past the end of iov. Fix this mess all up by using ea->ea_data as the base for the bounds check. An "untrusted" server can use this to leak up to 8 bytes of kernel heap into the EA name comparison and influence which WSL xattr the data is interpreted as.

osv:CVE-2026-31614

Kernel

Fixed versions: 6.6.136, 6.12.83, 6.18.24, 6.19.14, 7.0.1

Complete source record
{
  "id": "c0ab4204b66f7b18c729ae5c763139d66da20708e9ff3b0b5bbf6df454314e2e",
  "url": "https://osv.dev/vulnerability/CVE-2026-31614",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "smb: client: fix off-by-8 bounds check in check_wsl_eas()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: smb: client: fix off-by-8 bounds check in check_wsl_eas() The bounds check uses (u8 *)ea + nlen + 1 + vlen as the end of the EA name and value, but ea_data sits at offset sizeof(struct smb2_file_full_ea_info) = 8 from ea, not at offset 0. The strncmp() later reads ea->ea_data[0..nlen-1] and the value bytes follow at ea_data[nlen+1..nlen+vlen], so the actual end is ea->ea_data + nlen + 1 + vlen. Isn't pointer math fun? The earlier check (u8 *)ea > end - sizeof(*ea) only guarantees the 8-byte header is in bounds, but since the last EA is placed within 8 bytes of the end of the response, the name and value bytes are read past the end of iov. Fix this mess all up by using ea->ea_data as the base for the bounds check. An \"untrusted\" server can use this to leak up to 8 bytes of kernel heap into the EA name comparison and influence which WSL xattr the data is interpreted as.",
    "evidence": "osv:CVE-2026-31614",
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      ],
      "modified": "2026-10-28T02:30:37.227299232Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/3d8b9d06bd3ac4c6846f5498800b0f5f8062e53b",
        "https://git.kernel.org/stable/c/5cc0574c84aa73946ade587c41e81757b8b01cb5",
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  "source_id": "core-osv",
  "document_id": 504621,
  "published_at": "2026-04-24T14:42:34.153+00:00"
}