Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-10-06T00:00:00 kernel: smb: client: fix server->total_read for compound encrypted PDUs 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H CWE-20

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix server->total_read for compound encrypted PDUs In receive_encrypted_standard(), server->total_read is left at the full decrypted frame size when walking sub-PDUs of a compound encrypted frame. As a result, cifs_handle_standard() passes this full size to smb2_check_message(), causing the PDU length guards to incorrectly validate the entire compound frame instead of the current sub-PDU. This allows truncated non-last sub-PDUs to bypass length validation, leading to out-of-bounds reads in smb2_get_data_area_len(). Fix this by setting server->total_read to the true length of the current sub-PDU: next_cmd for non-last sub-PDUs, and the remaining pdu_length for the last one.

A flaw was found in the Linux kernel's SMB client. When processing compound encrypted Protocol Data Units (PDUs), the client incorrectly validates the length of individual messages within the compound frame. A malicious or compromised SMB server can exploit this flaw by returning truncated sub-PDUs, triggering an out-of-bounds read during response handling. This vulnerability primarily results in a system crash and Denial of Service (DoS), or potentially the disclosure of sensitive kernel memory.

The SMB client can validate an encrypted compound response against the size of the complete decrypted frame instead of the size of the current sub-PDU. A malicious or compromised SMB server can send a truncated non-last sub-PDU with a crafted NextCommand value so that smb2_check_message accepts it and smb2_get_data_area_len performs an out-of-bounds read. For the CVSS the PR:N value is used because the attacker needs no privileges on the affected client and only needs control of an SMB server used by that client. The issue is network reachable after an SMB session has been established and can cause a client kernel crash or denial of service. The paranoid score also considers limited confidentiality impact from the out-of-bounds read. There is no demonstrated write primitive, so integrity impact and privilege escalation are not included in the score. SMB services are commonly limited to internal or enterprise networks, but a compromised trusted file server can still expose many connected clients. Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability. Red Hat Enterprise Linux 10 Fix deferred kernel Red Hat Enterprise Linux 6 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel-rt Red Hat Enterprise Linux 8 Fix deferred kernel Red Hat Enterprise Linux 8 Fix deferred kernel-rt Red Hat Enterprise Linux 9 Fix deferred kernel Red Hat Enterprise Linux 9 Fix deferred kernel-rt Red Hat OpenShift Container Platform 4 Fix deferred openshift/ose-rhel-coreos-8 Red Hat OpenShift Container Platform 4 Fix deferred openshift/ose-rhel-coreos-9 https://www.cve.org/CVERecord?id=CVE-2026-98167 https://nvd.nist.gov/vuln/detail/CVE-2026-98167 https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98167.mbox https://kernelcve.org/list/?q=CVE-2026-98167