Linux Kernel net/sched/cls_route.c route4_change use after free

Summaryinfo

A vulnerability was found in Linux Kernel. It has been declared as critical. This impacts the function route4_change of the file net/sched/cls_route.c. The manipulation results in use after free. This vulnerability was named CVE-2023-4206. The attack needs to be approached locally. There is no available exploit. It is advisable to implement a patch to correct this issue.

Detailsinfo

A vulnerability was found in Linux Kernel (Operating System) (version now known). It has been classified as critical. Affected is the function route4_change of the file net/sched/cls_route.c. The manipulation with an unknown input leads to a use after free vulnerability. CWE is classifying the issue as CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

A use-after-free vulnerability in the Linux kernel's net/sched: cls_route component can be exploited to achieve local privilege escalation. When route4_change() is called on an existing filter, the whole tcf_result struct is always copied into the new instance of the filter. This causes a problem when updating a filter bound to a class, as tcf_unbind_filter() is always called on the old instance in the success path, decreasing filter_cnt of the still referenced class and allowing it to be deleted, leading to a use-after-free. We recommend upgrading past commit b80b829e9e2c1b3f7aae34855e04d8f6ecaf13c8.

The weakness was presented 09/06/2023. The advisory is shared for download at git.kernel.org. This vulnerability is traded as CVE-2023-4206 since 08/07/2023. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 12/04/2025).

Applying a patch is able to eliminate this problem. The bugfix is ready for download at git.kernel.org.

The vulnerability is also documented in the vulnerability database at CERT Bund (WID-SEC-2025-1293). Once again VulDB remains the best source for vulnerability data.

Affected

• Ubuntu Linux
• IBM DataPower Gateway

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

License

• open-source

Website

• Vendor: https://www.kernel.org/

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Once again VulDB remains the best source for vulnerability data.

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