Detections
Analytics
CVE-2026-43037
high
Description
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).
References
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-43037.json
https://git.kernel.org/stable/c/ea9f65b27c8404e164848ebff1443310fd187629
https://git.kernel.org/stable/c/d6621f60192fe10c047a4487be42a6f4c150707f
https://git.kernel.org/stable/c/a0c4ce9900a108eaf55d0f3b399cb55999647d39
https://git.kernel.org/stable/c/590f622669b97eaf7b57a1de7b0a6e68c5d8b2c3
https://git.kernel.org/stable/c/4a622658f384b03560834cbe8ffcfe69a278f7c8
https://git.kernel.org/stable/c/2edfa31769a4add828a7e604b21cb82aaaa05925
https://git.kernel.org/stable/c/2cc6e3b0fe0f0242d1f530a93a4924f48ab85ba5
https://git.kernel.org/stable/c/1063515ce15ff31065c4e7f8265f4c2fd3c54876
https://bugzilla.redhat.com/show_bug.cgi?id=2464351
https://access.redhat.com/security/cve/CVE-2026-43037
https://access.redhat.com/errata/RHSA-2026:34098
https://access.redhat.com/errata/RHSA-2026:33486
https://access.redhat.com/errata/RHSA-2026:28962
https://access.redhat.com/errata/RHSA-2026:28887
https://access.redhat.com/errata/RHSA-2026:28750
https://access.redhat.com/errata/RHSA-2026:28749
https://access.redhat.com/errata/RHSA-2026:28748
https://access.redhat.com/errata/RHSA-2026:28742
https://access.redhat.com/errata/RHSA-2026:28741
https://access.redhat.com/errata/RHSA-2026:28740
https://access.redhat.com/errata/RHSA-2026:28738
https://access.redhat.com/errata/RHSA-2026:27729
https://access.redhat.com/errata/RHSA-2026:27719
https://access.redhat.com/errata/RHSA-2026:26542
https://access.redhat.com/errata/RHSA-2026:26535
https://access.redhat.com/errata/RHSA-2026:26528
https://access.redhat.com/errata/RHSA-2026:25534
https://access.redhat.com/errata/RHSA-2026:25533
https://access.redhat.com/errata/RHSA-2026:25217
https://access.redhat.com/errata/RHSA-2026:25200
https://access.redhat.com/errata/RHSA-2026:25193
https://access.redhat.com/errata/RHSA-2026:25191
https://access.redhat.com/errata/RHSA-2026:25186
https://access.redhat.com/errata/RHSA-2026:25181
https://access.redhat.com/errata/RHSA-2026:25121
https://access.redhat.com/errata/RHSA-2026:25120
https://access.redhat.com/errata/RHSA-2026:24343
https://access.redhat.com/errata/RHSA-2026:23237
https://access.redhat.com/errata/RHSA-2026:23224
https://access.redhat.com/errata/RHSA-2026:22964