Tracker / CVE-2026-43037
CVE-2026-43037
In the Linux kernel, the following vulnerability has been resolved: ip6_tunnel: clear skb2->cb[] in ip4ip6_err() Oskar Kjos reported the following problem. ip4ip6_err() calls icmp_send() on a cloned skb whose cb[] was written by the IPv6 receive path as struct inet6_skb_parm. icmp_send() passes IPCB(skb2) to __ip_options_echo(), which interprets that cb[] region as struct inet_skb_parm (IPv4). The layouts differ: inet6_skb_parm.nhoff at offset 14 overlaps inet_skb_parm.opt.rr, producing 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 (IP_OPTIONS_DATA_FIXED_SIZE). To fix this we clear skb2->cb[], as suggested by Oskar Kjos. Also add minimal IPv4 header validation (version == 4, ihl >= 5).
Affected products and versions
| linux | linux_kernel |
|---|---|
| linux | linux_kernel · 2.6.22 → 5.10.253 |
| linux | linux_kernel · 5.11 → 5.15.203 |
| linux | linux_kernel · 5.16 → 6.1.168 |
| linux | linux_kernel · 6.13 → 6.18.22 |
| linux | linux_kernel · 6.19 → 6.19.12 |
| linux | linux_kernel · 6.2 → 6.6.134 |
| linux | linux_kernel · 6.7 → 6.12.81 |