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CVE-2026-43037 is a Linux kernel vulnerability in the ip6_tunnel subsystem, specifically in ip4ip6_err(). The flaw occurs when ip4ip6_err() calls icmp_send() on a cloned skb whose cb[] control buffer was previously populated by the IPv6 receive path as struct inet6_skb_parm. Later, icmp_send() passes IPCB(skb2) to __ip_options_echo(), which interprets the same cb[] region as struct inet_skb_parm for IPv4 processing. Because the IPv6 and IPv4 skb control-buffer layouts differ, inet6_skb_parm.nhoff at offset 14 overlaps inet_skb_parm.opt.rr, which can yield a non-zero rr value. __ip_options_echo() then reads optlen from attacker-controlled packet data at sptr[rr+1] and copies that many bytes into dopt->__data, a fixed 40-byte stack buffer defined by IP_OPTIONS_DATA_FIXED_SIZE. This creates a stack-based buffer overflow condition in kernel context. The upstream fix clears skb2->cb[] before reuse and adds minimal IPv4 header validation requiring version == 4 and ihl >= 5.
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No public exploit code observed for this vulnerability.
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16 sources tracked across advisories and community write-ups. News coverage will land here when it surfaces.
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Every observed campaign linking this CVE to a named adversary.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.