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.
Published: 2026-10-18
Score: n/a
EPSS: < 1% Very Low
KEV: No
Impact: Information Disclosure via Out-of-Bounds Read
Action: Immediate Patch
AI Analysis

Impact

The SMB client in the Linux kernel fails to enforce bounds when parsing create-context structures in SMB2 requests. A malicious SMB server can craft a chain of contexts that causes the kernel to read memory beyond the intended bounds, potentially exposing adjacent kernel memory contents. Similar parsing errors in SMB2/SMB3 lease handling allow the kernel to interpret non-canonical offsets, which can also lead to unintended data reads. These weaknesses ultimately enable an attacker to acquire sensitive information from the kernel, rather than execute code directly.

Affected Systems

All Linux kernel installations that contain the SMB client component are potentially affected. No specific version range is provided, so any kernel that has not incorporated the upstream patch remains vulnerable. Systems running upstream kernels or backports lacking the fix are at risk, regardless of distribution.

Risk and Exploitability

The vulnerability does not provide direct remote code execution; its primary impact is confidentiality loss through out‑of‑bounds reads. The EPSS metric is not available in the advisory, and the issue is not listed in the CISA KEV catalog. While the lack of a direct execution path reduces immediate urgency compared to higher‑severity flaws, the potential to leak kernel memory makes swift mitigation desirable.

Generated by OpenCVE AI on October 18, 2026 at 23:47 UTC.

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

  • Apply a kernel update that contains the SMB client parsing fix (e.g., upgrade to a version after the patch commit 05a7fd8)
  • If an immediate kernel upgrade is not possible, disable the SMB client kernel module or prevent it from loading
  • Configure network firewalls or host policies to block SMB traffic to untrusted or unknown servers

Generated by OpenCVE AI on October 18, 2026 at 23:47 UTC.

Tracking

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Advisories

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History

Sun, 18 Oct 2026 15:30:00 +0000

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

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-10-19T09:19:49.737Z

Reserved: 2026-09-25T10:25:14.350Z

Link: CVE-2026-98454

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-18T16:16:55.757

Modified: 2026-10-19T10:18:54.673

Link: CVE-2026-98454

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-19T00:00:10Z

Weaknesses

No weakness.