Linux Kernel up to 7.2.6/7.3-rc1 BPF bpf_refcount_acquire reference count

Summaryinfo

A vulnerability classified as very critical was found in Linux Kernel up to 7.2.6/7.3-rc1. This impacts the function bpf_refcount_acquire of the component BPF. The manipulation results in reference count. This vulnerability was named CVE-2026-98038. The attack may be performed from remote. There is no available exploit. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.2.6/7.3-rc1. It has been classified as very critical. Affected is the function bpf_refcount_acquire of the component BPF. The manipulation with an unknown input leads to a reference count vulnerability. CWE is classifying the issue as CWE-911. The product uses a reference count to manage a resource, but it does not update or incorrectly updates the reference count. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: bpf: Keep refcount_acquire nullable for borrowed RCU kptrs bpf_refcount_acquire() is fallible for a borrowed reference because the object may have reached a zero refcount. The verifier therefore keeps KF_RET_NULL on the return value unless the argument is an owning reference. An RCU-protected load of a local kptr is marked MEM_ALLOC, but it only receives NON_OWN_REF when the pointee contains a graph node. A refcounted object without a graph node consequently looks like an owning reference even though the loaded register has no acquired reference state. If the program drops the last real reference while remaining in the RCU critical section, refcount_inc_not_zero() returns NULL while the verifier treats the result as non-NULL. Only classify the argument as owning when it is backed by a verifier-tracked reference. This retains the non-NULL return for pointers from bpf_obj_new(), bpf_kptr_xchg(), or an earlier successful acquisition, while requiring a NULL check for borrowed RCU kptrs. [ kkd: Rewrote commit log ]

The advisory is available at git.kernel.org. This vulnerability is traded as CVE-2026-98038 since 09/25/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. Additional levels of successful authentication are necessary 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 85074498228a2500ea8b8039c49cc1ab8ad5328f/dc36739e5cc9f60485418a910b42bc95339218d2 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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Entryinfo

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