UBUNTU-CVE-2026-98454: High severity ubuntu/linux vulnerability
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.
- Upgrade
Upgrade
ubuntu/linux-hwe-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42~24.04.1 - Upgrade
Upgrade
ubuntu/linux-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1~24.04.1 - Upgrade
Upgrade
ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-42.42 - Upgrade
Upgrade
ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1016.17 - Upgrade
Upgrade
ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1016.18 - Upgrade
Upgrade
ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
Upgrade
ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
Upgrade
ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1015.16 - Upgrade
Upgrade
ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1 - Compensating control
In smb2_parse_contexts(), bound each create-context name range to the current context and each context to its Next field; reject offsets before the context header and malformed chains, and do not dispatch a known handler when DataLength is zero.
- Compensating control
Parse SMB2/SMB3 lease contexts from DataOffset and require DataLength to match the v1 or v2 lease_context size used by ksmbd; read QFid DiskFileId only when the context data covers that field, and read LeaseState and LeaseFlags at DataOffset rather than canonical offsets.
Event History
Frequently Asked Questions
Which systems are exposed to this issue?
The affected software list includes Ubuntu linux, linux-fips, linux-aws, linux-azure, linux-gcp, and their listed FIPS variants. Exposure is relevant where the kernel SMB client processes SMB2 or SMB3 create-context responses from an SMB server.
What does an attacker need to exploit it?
An attacker needs to cause the SMB client to process a malformed SMB2/SMB3 create-context chain. The vector is network-based, requires low attack complexity, no privileges, and user interaction according to the supplied severity vector.
What is the security impact?
The supplied vector indicates high availability impact, with no direct confidentiality or integrity impact. Malformed context records can cause out-of-bounds reads by context handlers before the fix.
How does the fix handle malformed lease contexts?
The corrected parser reads lease data from DataOffset and requires DataLength to match the expected v1 or v2 lease context size. A lease-size mismatch skips lease parsing rather than failing the SMB open operation.