Bug 2521415 (CVE-2026-74608)

Summary: CVE-2026-74608 kernel: smb: client: Fix use-after-free in cifs_try_adding_channels()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Server Message Block (SMB) client of the Linux kernel. A use-after-free vulnerability exists in the `cifs_try_adding_channels()` function. This occurs when a concurrent interface list refresh removes a reference to an interface while a channel creation is in progress and fails, leading to the system attempting to access memory that has already been freed. This could result in a denial of service or potentially lead to arbitrary code execution.
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Description OSIDB Bzimport 2026-08-22 15:44:28 UTC 
In the Linux kernel, the following vulnerability has been resolved:

smb: client: Fix use-after-free in cifs_try_adding_channels()

cifs_try_adding_channels() takes a temporary reference to an interface
before dropping iface_lock. If cifs_ses_add_channel() fails, it drops
that reference and then increments iface->weight_fulfilled.

A concurrent interface list refresh can remove the list reference while
channel creation is in progress. In that case, the failure-path
kref_put() releases the last reference and frees iface. Updating
weight_fulfilled afterward then accesses freed memory.

Increment weight_fulfilled before dropping the temporary reference,
keeping iface alive for the final access.
Comment 1 Mauro Matteo Cascella 2026-08-24 12:53:13 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026082216-CVE-2026-74608-dfb0@gregkh/T