cbcvebase.
CVE-2026-43037
published 2026-05-01

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…

PriorityP355critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
EPSS
0.56%
43.4th percentile
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

71 ranges· showing 25
VendorProductVersion rangeFixed in
linuxlinux
linuxlinux>= c4d3efafcc933fd2ffd169d7dc4f980393a13796 < ea9f65b27c8404e164848ebff1443310fd187629ea9f65b27c8404e164848ebff1443310fd187629
linuxlinux>= c4d3efafcc933fd2ffd169d7dc4f980393a13796 < d6621f60192fe10c047a4487be42a6f4c150707fd6621f60192fe10c047a4487be42a6f4c150707f
linuxlinux>= c4d3efafcc933fd2ffd169d7dc4f980393a13796 < 2cc6e3b0fe0f0242d1f530a93a4924f48ab85ba52cc6e3b0fe0f0242d1f530a93a4924f48ab85ba5
linuxlinux>= c4d3efafcc933fd2ffd169d7dc4f980393a13796 < a0c4ce9900a108eaf55d0f3b399cb55999647d39a0c4ce9900a108eaf55d0f3b399cb55999647d39
linuxlinux>= c4d3efafcc933fd2ffd169d7dc4f980393a13796 < 1063515ce15ff31065c4e7f8265f4c2fd3c548761063515ce15ff31065c4e7f8265f4c2fd3c54876
linuxlinux>= c4d3efafcc933fd2ffd169d7dc4f980393a13796 < 590f622669b97eaf7b57a1de7b0a6e68c5d8b2c3590f622669b97eaf7b57a1de7b0a6e68c5d8b2c3
linuxlinux>= c4d3efafcc933fd2ffd169d7dc4f980393a13796 < 4a622658f384b03560834cbe8ffcfe69a278f7c84a622658f384b03560834cbe8ffcfe69a278f7c8
linuxlinux>= c4d3efafcc933fd2ffd169d7dc4f980393a13796 < 2edfa31769a4add828a7e604b21cb82aaaa059252edfa31769a4add828a7e604b21cb82aaaa05925
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel>= 2.6.22 < 5.10.2535.10.253
linuxlinux_kernel>= 5.11 < 5.15.2035.15.203
linuxlinux_kernel>= 5.16 < 6.1.1686.1.168
linuxlinux_kernel>= 6.13 < 6.18.226.18.22
linuxlinux_kernel>= 6.19 < 6.19.126.19.12
linuxlinux_kernel>= 6.2 < 6.6.1346.6.134
linuxlinux_kernel>= 6.7 < 6.12.816.12.81
ubuntulinux
ubuntulinux-aws

CVSS provenance

nvdv3.19.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
vendor_ubuntu8.8HIGH
vendor_redhat7.0HIGH
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