CVE-2025-68725
Unknown Unknown - Not Provided
Invalid GSO Type Handling in Linux Kernel BPF Causes Offload Warning

Publication date: 2025-12-24

Last updated on: 2026-02-26

Assigner: kernel.org

Description
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.
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Meta Information
Published
2025-12-24
Last Modified
2026-02-26
Generated
2026-05-07
AI Q&A
2025-12-24
EPSS Evaluated
2026-05-05
NVD
CVE-2025-68725
Affected Vendors & Products
Showing 6 associated CPEs
Vendor Product Version / Range
linux linux_kernel From 5.11 (inc) to 5.15.199 (exc)
linux linux_kernel From 5.16 (inc) to 6.1.162 (exc)
linux linux_kernel From 6.2 (inc) to 6.6.122 (exc)
linux linux_kernel From 5.6 (inc) to 5.10.249 (exc)
linux linux_kernel From 6.13 (inc) to 6.18.2 (exc)
linux linux_kernel From 6.7 (inc) to 6.12.68 (exc)
Helpful Resources
Exploitability
CWE
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CWE ID Description
CWE-UNKNOWN
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AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability involves the Linux kernel's BPF (Berkeley Packet Filter) test infrastructure emitting invalid GSO (Generic Segmentation Offload) types to the network stack. Specifically, when a BPF program uses bpf_clone_redirect() to push packets to the loopback device, malformed GSO properties occur because gso_type is not properly set, leading to warnings and potentially incorrect handling of packets. The issue arises from convert___skb_to_skb() setting gso_segs and gso_size but not gso_type, which can cause offload features to be disabled or misused. The fix rejects such malformed packets at the point of emission to prevent further issues.


How can this vulnerability impact me? :

This vulnerability can cause the Linux kernel to process network packets with malformed GSO properties, potentially leading to offload warnings and disabling of GSO-related features. While it does not explicitly state a direct exploit, malformed packets could affect network performance or stability by triggering warnings and disabling optimizations. It may also open a vector for malicious actors to send crafted packets that bypass normal checks, although the fix aims to reject such packets early.


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