Linux Kernel up to 6.18.1 skb_warn_bad_offload privilege escalation

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.18.1 and classified as problematic. The impacted element is the function skb_warn_bad_offload. The manipulation results in an unknown weakness. This vulnerability is reported as CVE-2025-68725. No exploit exists. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic has been found in Linux Kernel up to 6.18.1. The impact remains unknown. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: bpf: Do not let BPF test infra emit invalid GSO types to stack Yinhao et al. reported that their fuzzer tool was able to trigger a skb_warn_bad_offload() from netif_skb_features() -> gso_features_check(). When a BPF program - triggered via BPF test infra - pushes the packet to the loopback device via bpf_clone_redirect() then mentioned offload warning can be seen. GSO-related features are then rightfully disabled. We get into this situation due to convert___skb_to_skb() setting gso_segs and gso_size but not gso_type. Technically, it makes sense that this warning triggers since the GSO properties are malformed due to the gso_type. Potentially, the gso_type could be marked non-trustworthy through setting it at least to SKB_GSO_DODGY without any other specific assumptions, but that also feels wrong given we should not go further into the GSO engine in the first place. The checks were added in 121d57af308d ("gso: validate gso_type in GSO handlers") because there were malicious (syzbot) senders that combine a protocol with a non-matching gso_type. If we would want to drop such packets, gso_features_check() currently only returns feature flags via netif_skb_features(), so one location for potentially dropping such skbs could be validate_xmit_unreadable_skb(), but then otoh it would be an additional check in the fast-path for a very corner case. Given bpf_clone_redirect() is the only place where BPF test infra could emit such packets, lets reject them right there.

The advisory is available at git.kernel.org. This vulnerability is traded as CVE-2025-68725 since 12/24/2025. 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 02/26/2026).

The vulnerability scanner Nessus provides a plugin with the ID 279716 (Linux Distros Unpatched Vulnerability : CVE-2025-68725), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.18.2 or 6.19-rc1 eliminates this vulnerability. Applying the patch fbea4c63b5385588cb44ab21f91e55e33c719a54/04a899573fb87273a656f178b5f920c505f68875 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (279716) and CERT Bund (WID-SEC-2025-2920). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Affected

• Open Source Linux Kernel

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.18.0
• 6.18.1

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

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CPE 2.2info

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Entryinfo

If you want to get best quality of vulnerability data, you may have to visit VulDB.

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