Bug 2492778 (CVE-2026-53247)

Summary: CVE-2026-53247 kernel: net: ethernet: mtk_eth_soc: Fix use-after-free in metadata dst teardown
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's ethernet driver for MediaTek (mtk_eth_soc) network devices. This vulnerability, a 'use-after-free', occurs when the system attempts to free a memory region while it is still being used by network packet processing. This can allow a local attacker to trigger system instability, potentially leading to a denial of service (DoS) or, in some cases, unauthorized code execution.
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Description OSIDB Bzimport 2026-06-25 10:05:16 UTC 
In the Linux kernel, the following vulnerability has been resolved:

net: ethernet: mtk_eth_soc: Fix use-after-free in metadata dst teardown

mtk_free_dev() calls metadata_dst_free() which frees the metadata_dst
with kfree() immediately, bypassing the RCU grace period.
In the RX path, skb_dst_set_noref() sets a non-refcounted pointer from
the skb to the metadata_dst. This function requires RCU read-side
protection and the dst must remain valid until all RCU readers complete.
Since metadata_dst_free() calls kfree() directly, a use-after-free can
occur if any skb still holds a noref pointer to the dst when the driver
tears it down.
Replace metadata_dst_free() with dst_release() which properly goes
through the refcount path: when the refcount drops to zero, it schedules
the actual free via call_rcu_hurry(), ensuring all RCU readers have
completed before the memory is freed.
Comment 1 Keith Grant 2026-06-26 00:07:53 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026062512-CVE-2026-53247-7eed@gregkh/T