CVE-2023-4208

Summary

CVE-2023-4208 is a use-after-free vulnerability affecting the net/sched: cls_u32 component in the Linux kernel. This issue can be exploited locally to achieve privilege escalation. When the u32_change() function is called to modify an existing filter, it creates a new instance of the filter by copying the entire tcf_result struct from the old one. However, when updating a filter bound to a class, tcf_unbind_filter() is called on the old instance in the success path, decreasing its filter_cnt and potentially allowing the referenced class to be deleted before the new filter is fully initialized. This leads to a use-after-free vulnerability. It is recommended to upgrade to commit 3044b16e7c6fe5d24b1cdbcf1bd0a9d92d1ebd81 to mitigate this issue.

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