Bug 2492286 (CVE-2026-53011)

Summary: CVE-2026-53011 kernel: net/sched: taprio: fix use-after-free in advance_sched() on schedule switch
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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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 Linux kernel's networking scheduler, specifically within the `taprio` module. When the system attempts to switch schedules, a use-after-free vulnerability occurs in the `advance_sched()` function. This happens because a pointer to an old schedule entry is still used after the memory for that entry has been queued for release. An attacker could potentially exploit this memory corruption to cause a denial of service or achieve arbitrary code execution.
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Description OSIDB Bzimport 2026-06-24 18:03:16 UTC 
In the Linux kernel, the following vulnerability has been resolved:

net/sched: taprio: fix use-after-free in advance_sched() on schedule switch

In advance_sched(), when should_change_schedules() returns true,
switch_schedules() is called to promote the admin schedule to oper.
switch_schedules() queues the old oper schedule for RCU freeing via
call_rcu(), but 'next' still points into an entry of the old oper
schedule. The subsequent 'next->end_time = end_time' and
rcu_assign_pointer(q->current_entry, next) are use-after-free.

Fix this by selecting 'next' from the new oper schedule immediately
after switch_schedules(), and using its pre-calculated end_time.
setup_first_end_time() sets the first entry's end_time to
base_time + interval when the schedule is installed, so the value
is already correct.

The deleted 'end_time = sched_base_time(admin)' assignment was also
harmful independently: it would overwrite the new first entry's
pre-calculated end_time with just base_time.
Comment 1 Mauro Matteo Cascella 2026-06-25 15:21:47 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026062449-CVE-2026-53011-6b0a@gregkh/T