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

Summaryinfo

A vulnerability, which was classified as very critical, has been found in Linux Kernel up to 7.2.6/7.3-rc1. Affected by this issue is the function collect_linked_regs of the component BPF. This manipulation causes race condition. This vulnerability is tracked as CVE-2026-98042. The attack is possible to be carried out remotely. No exploit exists. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as very critical was found in Linux Kernel up to 7.2.6/7.3-rc1. Affected by this vulnerability is the function collect_linked_regs of the component BPF. The manipulation with an unknown input leads to a race condition vulnerability. The CWE definition for the vulnerability is 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. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: bpf: Don't resurrect a scalar id dropped by collect_linked_regs() check_cond_jmp_op() copies the compared registers into env->{false,true}_reg{1,2} before collect_linked_regs() runs and copies those snapshots back into both branch states afterwards. collect_linked_regs() records at most LINKED_REGS_MAX members of a linked registers group in the jump history and calls clear_scalar_id() for every member that does not fit. The compared register is not exempt from that. As a consequence, sync_linked_regs() might adjust ranges for more registers than bpf_bt_sync_linked_regs() can propagate precision to. Collect the linked registers before the snapshots are taken instead. This might lead to some unnecessary clear_scalar_id's, but from previous testing situations with many linked registers are extremely rare.

The advisory is shared at git.kernel.org. This vulnerability is known as CVE-2026-98042 since 09/25/2026. The exploitation appears to be easy. The attack can be launched remotely. Additional levels of successful authentication are required for exploitation. Technical details are known, but no exploit is available. The price for an exploit might be around 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 e821ff19b8ef08255ff8d8234774ed814637e9bf/73a98f96811e2cb0f4210b1caa8cb322f92f2a2b 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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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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