Linux Kernel CVE-2026-31684: Nested VLAN header buffer over-read in act_csum
CVE-2026-31684 Published on April 25, 2026
net: sched: act_csum: validate nested VLAN headers
In the Linux kernel, the following vulnerability has been resolved:
net: sched: act_csum: validate nested VLAN headers
tcf_csum_act() walks nested VLAN headers directly from skb->data when an
skb still carries in-payload VLAN tags. The current code reads
vlan->h_vlan_encapsulated_proto and then pulls VLAN_HLEN bytes without
first ensuring that the full VLAN header is present in the linear area.
If only part of an inner VLAN header is linearized, accessing
h_vlan_encapsulated_proto reads past the linear area, and the following
skb_pull(VLAN_HLEN) may violate skb invariants.
Fix this by requiring pskb_may_pull(skb, VLAN_HLEN) before accessing and
pulling each nested VLAN header. If the header still is not fully
available, drop the packet through the existing error path.
Products Associated with CVE-2026-31684
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Affected Versions
Linux:- Version 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 and below a69738efea0996d05a3c7d2178551b891744df1b is affected.
- Version 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 and below ec4930979b3f7bbeb7af5744599fc6603a4dba62 is affected.
- Version 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 and below 3d165d975305cf76ff0b10a3c798fb31e5f5f9a5 is affected.
- Version 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 and below c842743d073bdd683606cb414eb0ca84465dd834 is affected.
- Version 3764bfae5056e95617b6ee074129297e11710886 is affected.
- Version 5.1 is affected.
- Before 5.1 is unaffected.
- Version 6.12.83, <= 6.12.* is unaffected.
- Version 6.18.24, <= 6.18.* is unaffected.
- Version 6.19.14, <= 6.19.* is unaffected.
- Version 7.0, <= * is unaffected.