Skip to main content

Boteraser | Website and Server Security Solutions

🛡️ CVE-2023-53477 — kernel

🟡 CVSS 5.5 — Medium ✅ No Known Exploit NVD
5.5
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

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

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().

How this vulnerability can be exploited

This issue can be reached with local access to the system, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

  • Attack vector: Local — a local account, shell or session on the host is needed.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: Low — an ordinary user account is enough.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: None.
  • Integrity impact: None.
  • Availability impact: High — total loss, or loss the attacker controls.

Affected software

CVE-2023-53477 is recorded against 2 packages.

  • kernel (from 6.2.0 up to 6.2.5)
  • linux-kernel (from 6.2 up to 6.2.5)

Timeline and source

Published on 1 October 2025 and last revised on 12 August 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
github.com (Advisory)
nvd.nist.gov (Advisory)
git.kernel.org (Package)

Other advisories for this package

kernel has other advisories on record. If you are patching this one, these are worth checking on the same host:

CVE-2023-53477 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity Medium
CVSS Score 5.5
CVSS Vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CWE N/A
Public Exploit ✅ No
Source NVD
Published 2025-10-01
Updated 2026-08-20
Modified 2026-08-12

Affected Packages

Software From version Fixed in
kernel 6.2.0 6.2.5
linux-kernel 6.2 6.2.5

Similar Threats

Vulnerability Monitoring

Track new vulnerabilities in kernel

CVE-2023-53477 is rated CVSS 5.5 Medium. BotEraser monitors your WordPress installation and notifies you when software you use appears in our vulnerability database.

Set Up Free Alerts →

No credit card required  ·  Results in minutes

ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

Browse related advisories

All advisoriesCVECVE 2023
✓