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CVE-2026-68121: pppoe: reload header pointer after dev_hard_header()

• Severity: high (CVSS 7.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-10 · updated 2026-10-19
• Weakness: CWE-416

Description

In the Linux kernel, the following vulnerability has been resolved: pppoe: reload header pointer after dev_hard_header() pppoe_sendmsg() saves a pointer to the PPPoE header before calling dev_hard_header(). Device header callbacks are allowed to reallocate the skb head, invalidating pointers into it. This can happen when a send is blocked in copy_from_user() while the first non-Ethernet port is added to an empty team device. The team's delegated GRE header callback then expands the skb head. PPPoE subsequently writes six bytes through the stale pointer into the freed head. Reload the PPPoE header through the skb's network-header offset after device header creation. pskb_expand_head() updates that offset when it relocates the head.

Affected products

• Linux kernel: 2.6.12 — 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/6866abf59976d273164a6624234d96a967280223
• https://git.kernel.org/stable/c/6eed5ae7887a93160803d2b81ff88e75eefd4a4c
• https://git.kernel.org/stable/c/7a56e7c9b08e08fd55a1bcada24cf4fe3782b722
• https://git.kernel.org/stable/c/7e9fbd7f96bcde63a7c798fe16b38cedee7a1501
• https://git.kernel.org/stable/c/ba3409369c5413cdf0dcbf3a928f76b48e8c3e6a
• https://git.kernel.org/stable/c/bed4caecd723693f750e13adbb2c42ca1249a3fd
• https://git.kernel.org/stable/c/e6493a4d1ee17595766165fa446d45b7e0c318d0
• https://git.kernel.org/stable/c/e9c238f6fe42fb1b4dba3a578277de32cb487937

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