UBUNTU-CVE-2026-53247
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.
02 / AFFECTED SOFTWARE
Affected packages
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13 explicit affected versions
43 explicit affected versions
16 explicit affected versions
5 explicit affected versions
10 explicit affected versions
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14 explicit affected versions
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03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
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.
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/80df409e1a483676826a6c66e693dba6ac507751
- https://git.kernel.org/stable/c/2d86aeb46d5f69c704065a8c69822582787272a1
- https://git.kernel.org/stable/c/459c6f35c58cf0fd5247e55d73ddaa29571d9b7e
- https://git.kernel.org/stable/c/72775977e89c25c99ee84d2c5baa3f86a8ba5cb4
- https://git.kernel.org/stable/c/80df409e1a483676826a6c66e693dba6ac507751
- https://git.kernel.org/stable/c/e634408d2b0cd939cfe019398a21fb47b7a8ffe3
- https://ubuntu.com/security/CVE-2026-53247
- https://ubuntu.com/security/notices/USN-8629-1
- https://ubuntu.com/security/notices/USN-8629-2
- https://ubuntu.com/security/notices/USN-8629-3
- https://ubuntu.com/security/notices/USN-8637-1
- https://ubuntu.com/security/notices/USN-8643-1
- https://www.cve.org/CVERecord?id=CVE-2026-53247