CVE-2026-53228

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

ipv6: sit: reload inner IPv6 header after GSO offloads

ipip6_tunnel_xmit() caches the inner IPv6 header pointer at function

entry and continues using it after iptunnel_handle_offloads().

For GSO skbs, iptunnel_handle_offloads() calls skb_header_unclone().

When the skb header is cloned, skb_header_unclone() can call

pskb_expand_head(), which may move the skb head. The pskb_expand_head()

contract requires pointers into the skb header to be reloaded after the

call.

If the later skb_realloc_headroom() branch is not taken, SIT uses the

stale iph6 pointer to read the inner hop limit and DS field. That can

read from a freed skb head after the old head's remaining clone is

released.

Reload iph6 after the offload helper succeeds and before subsequent

reads from the inner IPv6 header. Keep the existing reload after

skb_realloc_headroom(), since that branch can also replace the skb.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References