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CVE-2026-74668: packet: use consistent hard_header_len in TX_RING send path

• Severity: high (CVSS 7.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-22 · updated 2026-10-16

Description

In the Linux kernel, the following vulnerability has been resolved: packet: use consistent hard_header_len in TX_RING send path tpacket_snd() reads dev->hard_header_len independently for skb allocation and header construction in tpacket_fill_skb(). Concurrent netdevice reconfiguration can therefore make the reserved headroom smaller than the amount later pushed, or make copylen - hard_header_len negative. Snapshot hard_header_len once before processing ring frames and use it for the frame limit, headroom allocation, copy length, and skb construction. Pass the snapshot to tpacket_fill_skb(). The separate SOCK_DGRAM consistency problem between hard_header_len and header_ops->create is not addressed here.

Affected products

• Linux kernel: 2.6.31 — fixed in 7.2

How to fix

Upgrade to a fixed version: Linux kernel 7.2. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/016763e829cac37b3234eace86fd0a4c560de4a7
• https://git.kernel.org/stable/c/21b5953e7494c16a42e6cd8cf110e18d13ae4a6b
• https://git.kernel.org/stable/c/27e068d1b35dbec10a3cf268887c94407be4badc
• https://git.kernel.org/stable/c/2a73b2c37ee3060a880b53cd24783d93fc7be5f8
• https://git.kernel.org/stable/c/9c7e8ff48c377bef18c3d178748aea0575b69ede
• https://git.kernel.org/stable/c/d48ea5c9c4c34dc0df621f0e39ed3a16b644621a
• https://git.kernel.org/stable/c/d85d2fd54e901637c81d847811e03c662aee13cd
• https://git.kernel.org/stable/c/e79f59a8527a49078cfaf8fe8fb5fcefc20c76d2

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