CVE-2023-53477

published 2025-10-01

CVE-2023-53477: In the Linux kernel, the following vulnerability has been resolved: ipv6: Add lwtunnel encap size of all siblings in nexthop calculation In function…

Priority P4 20 medium 5.5 CVSS 3.1

AV L AC L PR L UI N S U C N I N A H

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

ipv6: Add lwtunnel encap size of all siblings in nexthop calculation

In function rt6_nlmsg_size(), the length of nexthop is calculated
by multipling the nexthop length of fib6_info and the number of
siblings. However if the fib6_info has no lwtunnel but the siblings
have lwtunnels, the nexthop length is less than it should be, and
it will trigger a warning in inet6_rt_notify() as follows:

WARNING: CPU: 0 PID: 6082 at net/ipv6/route.c:6180 inet6_rt_notify+0x120/0x130
......
Call Trace:

fib6_add_rt2node+0x685/0xa30
fib6_add+0x96/0x1b0
ip6_route_add+0x50/0xd0
inet6_rtm_newroute+0x97/0xa0
rtnetlink_rcv_msg+0x156/0x3d0
netlink_rcv_skb+0x5a/0x110
netlink_unicast+0x246/0x350
netlink_sendmsg+0x250/0x4c0
sock_sendmsg+0x66/0x70
___sys_sendmsg+0x7c/0xd0
__sys_sendmsg+0x5d/0xb0
do_syscall_64+0x3f/0x90
entry_SYSCALL_64_after_hwframe+0x72/0xdc

This bug can be reproduced by script:

ip -6 addr add 2002::2/64 dev ens2
ip -6 route add 100::/64 via 2002::1 dev ens2 metric 100

for i in 10 20 30 40 50 60 70;
do
ip link add link ens2 name ipv_$i type ipvlan
ip -6 addr add 2002::$i/64 dev ipv_$i
ifconfig ipv_$i up
done

for i in 10 20 30 40 50 60;
do
ip -6 route append 100::/64 encap ip6 dst 2002::$i via 2002::1
dev ipv_$i metric 100
done

ip -6 route append 100::/64 via 2002::1 dev ipv_70 metric 100

This patch fixes it by adding nexthop_len of every siblings using
rt6_nh_nlmsg_size().

Affected

17 ranges

Vendor	Product	Version range	Fixed in
debian	linux	< linux 6.1.20-1 (bookworm)	linux 6.1.20-1 (bookworm)
linux	linux	—	—
linux	linux	>= beb1afac518dec5a15dc92ba8f0ca016dcf457b4 < aba298b35619213ca787d08d472049627d8cd012	aba298b35619213ca787d08d472049627d8cd012
linux	linux	>= beb1afac518dec5a15dc92ba8f0ca016dcf457b4 < da26369377f0b671c14692e2d65ceb38131053e1	da26369377f0b671c14692e2d65ceb38131053e1
linux	linux	>= beb1afac518dec5a15dc92ba8f0ca016dcf457b4 < dcdddb5f490890d058ea1f194d661219e92fe88d	dcdddb5f490890d058ea1f194d661219e92fe88d
linux	linux	>= beb1afac518dec5a15dc92ba8f0ca016dcf457b4 < e11e4d524eba2d3c8fdf897d7ce3853f7573bae9	e11e4d524eba2d3c8fdf897d7ce3853f7573bae9
linux	linux	>= beb1afac518dec5a15dc92ba8f0ca016dcf457b4 < aa75d826c221e8d48607aef33836cf872a159cf1	aa75d826c221e8d48607aef33836cf872a159cf1
linux	linux	>= beb1afac518dec5a15dc92ba8f0ca016dcf457b4 < 4cc59f386991ec9374cb4bc83dbe1c0b5a95033f	4cc59f386991ec9374cb4bc83dbe1c0b5a95033f
linux	linux_kernel	>= 0 < 5.10.178-1	5.10.178-1
linux	linux_kernel	>= 0 < 6.1.20-1	6.1.20-1
linux	linux_kernel	>= 0 < 6.1.20-1	6.1.20-1
linux	linux_kernel	>= 0 < 6.1.20-1	6.1.20-1
linux	linux_kernel	>= 4.11 < 5.4.235	5.4.235
linux	linux_kernel	>= 5.11 < 5.15.100	5.15.100
linux	linux_kernel	>= 5.16 < 6.1.18	6.1.18
linux	linux_kernel	>= 5.5 < 5.10.173	5.10.173
linux	linux_kernel	>= 6.2 < 6.2.5	6.2.5

CVSS provenance

nvd v3.1 5.5 MEDIUM CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

osv 5.5 MEDIUM

vendor_debian 5.5 MEDIUM

vendor_redhat 5.5 MEDIUM

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