CVE-2023-53477: ipv6: Add lwtunnel encap size of all siblings in nexthop calculation
Vulnerability summary
CVE-2023-53477 is a medium (CVSS 5.5) vulnerability in linux. EPSS estimates a 0.16% chance of exploitation in the next 30 days, higher than 5.1% of scored vulnerabilities.
Not severe (CVSS 5.5, local access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 2 · Related 1Timeline
- 01-10-2025PublishedVulnerability first disclosed.
- 11-05-2026Last modifiedVulnerability information updated.
Description
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: <TASK> 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().
CVSS metrics
4 scores · 3 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.16%
Chance of exploitation in the next 30 days
Percentile
5%
Versus all other CVEs
30-day change
No change 0.00 pp
From 0.16% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeNo weakness data has been published for this record.
Affected systems
Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu122 products
- linuxAll versions (No fix recorded) | < 5.4.0-152.169 | < 5.15.0-79.86
- linux-allwinner-5.19All versions (No fix recorded)
- linux-awsAll versions (No fix recorded) | < 5.4.0-1104.112 | < 5.15.0-1042.47
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11All versions (No fix recorded)
Linux2 products
- linux≥ beb1afac518dec5a15dc92ba8f0ca016dcf457b4, < aba298b35619213ca787d08d472049627d8cd012 | ≥ beb1afac518dec5a15dc92ba8f0ca016dcf457b4, < da26369377f0b671c14692e2d65ceb38131053e1 | ≥ beb1afac518dec5a15dc92ba8f0ca016dcf457b4, < dcdddb5f490890d058ea1f194d661219e92fe88d | ≥ beb1afac518dec5a15dc92ba8f0ca016dcf457b4, < e11e4d524eba2d3c8fdf897d7ce3853f7573bae9 | ≥ beb1afac518dec5a15dc92ba8f0ca016dcf457b4, < aa75d826c221e8d48607aef33836cf872a159cf1 | ≥ beb1afac518dec5a15dc92ba8f0ca016dcf457b4, < 4cc59f386991ec9374cb4bc83dbe1c0b5a95033f | 4.11
- linux_kernel≥ 4.11, < 5.4.235 | ≥ 5.5, < 5.10.173 | ≥ 5.11, < 5.15.100 | ≥ 5.16, < 6.1.18 | ≥ 6.2, < 6.2.5
Debian1 product
- linux< 6.1.20-1
3 vendors · 125 products
