CVE-2026-98454

smb: client: fix create context out-of-bounds reads

Published Oct 18, 2026 CVSS 3.1 · 8.1 High EPSS < 1% KEV · Not listed
Description
In the Linux kernel, the following vulnerability has been resolved:

smb: client: fix create context out-of-bounds reads

smb2_parse_contexts() 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
lease_context size used by ksmbd. A size mismatch skips lease parsing
without failing the open.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4850-1 linux-6.12 security update
Ubuntu USN Ubuntu USN USN-9019-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9020-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9022-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9023-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9024-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9025-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9026-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9039-1 Linux kernel (Azure CVM) vulnerabilities
Ubuntu USN Ubuntu USN USN-9040-1 Linux kernel (Low Latency NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-9066-1 Linux kernel (HWE) vulnerabilities
Ubuntu USN Ubuntu USN USN-9091-1 Linux kernel (NVIDIA Tegra) vulnerabilities
History
Type Values Removed Values Added
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H'}

cvssV3_1

{'score': 8.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H'}

Type Values Removed Values Added
Weaknesses CWE-125
References
Metrics threat_severity

None

cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H'}

threat_severity

Moderate

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: smb: client: fix create context out-of-bounds reads smb2_parse_contexts() 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 lease_context size used by ksmbd. A size mismatch skips lease parsing without failing the open.
Title smb: client: fix create context out-of-bounds reads
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Linux
Published
Updated
Oct 30, 2026, 12:38 PM
Reserved
Sep 25, 2026, 10:25 AM
Status
Received
Published
Oct 18, 2026, 4:16 PM
Modified
Oct 30, 2026, 1:21 PM
Severity
Moderate
Public date
Oct 18, 2026, 12:00 AM