Bug 2468216 (CVE-2026-43424)

Summary: CVE-2026-43424 kernel: usb: gadget: f_tcm: Fix NULL pointer dereferences in nexus handling
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: unspecified    
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 Linux kernel's USB gadget subsystem (f_tcm). A malicious or misconfigured USB host can exploit a race condition by sending specific Bulk-Only Transport (BOT) commands. This can trigger a NULL pointer dereference, leading to a kernel panic and a local Denial of Service (DoS) on the affected system.
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Description OSIDB Bzimport 2026-05-08 15:05:16 UTC 
In the Linux kernel, the following vulnerability has been resolved:

usb: gadget: f_tcm: Fix NULL pointer dereferences in nexus handling

The `tpg->tpg_nexus` pointer in the USB Target driver is dynamically
managed and tied to userspace configuration via ConfigFS. It can be
NULL if the USB host sends requests before the nexus is fully
established or immediately after it is dropped.

Currently, functions like `bot_submit_command()` and the data
transfer paths retrieve `tv_nexus = tpg->tpg_nexus` and immediately
dereference `tv_nexus->tvn_se_sess` without any validation. If a
malicious or misconfigured USB host sends a BOT (Bulk-Only Transport)
command during this race window, it triggers a NULL pointer
dereference, leading to a kernel panic (local DoS).

This exposes an inconsistent API usage within the module, as peer
functions like `usbg_submit_command()` and `bot_send_bad_response()`
correctly implement a NULL check for `tv_nexus` before proceeding.

Fix this by bringing consistency to the nexus handling. Add the
missing `if (!tv_nexus)` checks to the vulnerable BOT command and
request processing paths, aborting the command gracefully with an
error instead of crashing the system.
Comment 1 Keith Grant 2026-05-08 23:20:17 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026050848-CVE-2026-43424-0d0d@gregkh/T