CVE-2026-98454: smb: client: fix create context out-of-bounds reads
In the Linux kernel, the following vulnerability has been resolved:
smb: client: fix create context out-of-bounds reads
smb2parsecontexts() validates the complete create-context area but does not limit each record to its Next field before dispatching it. A malformed chain can therefore expose bytes beyond the current context to a handler. The QFid handler also used a full response-structure cast although it only reads DiskFileId.
The SMB2/SMB3 lease parsers made the same layout assumption: they read LeaseState and LeaseFlags at canonical offsets rather than at DataOffset. A valid non-canonical DataOffset could therefore yield unrelated in-bounds data, while a short DataLength was still accepted.
Limit each context to its Next value, reject offsets before the context header, and reject malformed chains. Bound the name range by the current context and do not dispatch a known handler when DataLength is zero. Read the QFid DiskFileId only when the context data covers that field. Parse the lease context from DataOffset and require DataLength to match the v1 or v2 leasecontext size used by ksmbd. A size mismatch skips lease parsing without failing the open.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Compensating control
Harden SMB2/SMB3 create-context parsing: bound each context and its name range by the current DataOffset and Next value, reject offsets before the current context and malformed chains, do not dispatch a known handler when DataLength is zero, parse lease fields from DataOffset only when DataLength exactly matches the ksmbd lease_context v1 or v2 size, and have the QFid handler read DiskFileId only when the context data covers that field.