Linux Kernel up to 7.2.6/7.3-rc1 BPF rhtab_map_update_existing/rhtab_delete_elem race condition

Summaryinfo

A vulnerability categorized as very critical has been discovered in Linux Kernel up to 7.2.6/7.3-rc1. The impacted element is the function rhtab_map_update_existing/rhtab_delete_elem of the component BPF. Such manipulation leads to race condition. This vulnerability is traded as CVE-2026-98035. An attack has to be approached locally. There is no exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.2.6/7.3-rc1 and classified as very critical. Affected by this issue is the function rhtab_map_update_existing/rhtab_delete_elem of the component BPF. The manipulation with an unknown input leads to a race condition vulnerability. Using CWE to declare the problem leads to CWE-362. The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently. Impacted is confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: bpf: Cancel special fields when recycling rhtab elements rhtab_map_update_existing() and rhtab_delete_elem() call bpf_obj_free_fields() when replacing or deleting a value. These map operations can run from BPF programs in NMI context, where releasing a referenced kptr or another complex field is not generally safe. Array and hash maps avoid that problem by cancelling only the asynchronous fields which can be stopped safely in the caller context. Other ownership state remains attached to the allocation until its memory allocator destructor performs the final cleanup. Use bpf_obj_cancel_fields() for the corresponding rhtab paths as well. This cancels timers, workqueues, and task work while allowing rhtab_mem_dtor() to release referenced kptrs when the allocation is eventually destroyed. [ kkd: Rebased, used direct helper calls, and rewrote the commit log ]

The advisory is available at git.kernel.org. This vulnerability is handled as CVE-2026-98035 since 09/25/2026. The exploitation is known to be easy. Local access is required to approach this attack. Additional levels of successful authentication are needed for exploitation. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 09/25/2026).

Upgrading to version 7.2.7 or 7.3-rc2 eliminates this vulnerability. Applying the patch 28fde1356dbc35e20a9f22a5ee65af09698fdf92/65cc95eba9e8b46312cac38c227473605a4b996a is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.2.0
• 7.2.1
• 7.2.2
• 7.2.3
• 7.2.4
• 7.2.5
• 7.2.6
• 7.3-rc1

License

• open-source

Website

• Vendor: https://www.kernel.org/

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