Linux Kernel up to 6.2.4 ipv6 net/ipv6/route.c rt6_nlmsg_size privilege escalation

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
4.9	$0-$5k	0.00

Summaryinfo

A vulnerability described as critical has been identified in Linux Kernel up to 5.4.234/5.10.172/5.15.99/6.1.17/6.2.4. This vulnerability affects the function rt6_nlmsg_size of the file net/ipv6/route.c of the component ipv6. The manipulation results in an unknown weakness. This vulnerability is cataloged as CVE-2023-53477. There is no exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability, which was classified as critical, was found in Linux Kernel up to 5.4.234/5.10.172/5.15.99/6.1.17/6.2.4. Affected is the function rt6_nlmsg_size of the file net/ipv6/route.c of the component ipv6. The impact remains unknown. CVE summarizes:

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().

The advisory is shared for download at git.kernel.org. This vulnerability is traded as CVE-2023-53477 since 10/01/2025. The exploitability is told to be difficult. There are known technical details, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 276910 (SUSE SLES12 Security Update : kernel (SUSE-SU-2025:4189-1)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.4.235, 5.10.173, 5.15.100, 6.1.18 or 6.2.5 eliminates this vulnerability. Applying the patch aba298b35619213ca787d08d472049627d8cd012/da26369377f0b671c14692e2d65ceb38131053e1/dcdddb5f490890d058ea1f194d661219e92fe88d/e11e4d524eba2d3c8fdf897d7ce3853f7573bae9/aa75d826c221e8d48607aef33836cf872a159cf1/4cc59f386991ec9374cb4bc83dbe1c0b5a95033f is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (276910) and CERT Bund (WID-SEC-2025-2187). Once again VulDB remains the best source for vulnerability data.

Affected

• Amazon Linux 2
• Red Hat Enterprise Linux
• SUSE Linux
• Oracle Linux
• Open Source Linux Kernel
• Dell Secure Connect Gateway

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 5.4.234
• 5.10.172
• 5.15.0
• 5.15.1
• 5.15.2
• 5.15.3
• 5.15.4
• 5.15.5
• 5.15.6
• 5.15.7
• 5.15.8
• 5.15.9
• 5.15.10
• 5.15.11
• 5.15.12
• 5.15.13
• 5.15.14
• 5.15.15
• 5.15.16
• 5.15.17
• 5.15.18
• 5.15.19
• 5.15.20
• 5.15.21
• 5.15.22
• 5.15.23
• 5.15.24
• 5.15.25
• 5.15.26
• 5.15.27
• 5.15.28
• 5.15.29
• 5.15.30
• 5.15.31
• 5.15.32
• 5.15.33
• 5.15.34
• 5.15.35
• 5.15.36
• 5.15.37
• 5.15.38
• 5.15.39
• 5.15.40
• 5.15.41
• 5.15.42
• 5.15.43
• 5.15.44
• 5.15.45
• 5.15.46
• 5.15.47
• 5.15.48
• 5.15.49
• 5.15.50
• 5.15.51
• 5.15.52
• 5.15.53
• 5.15.54
• 5.15.55
• 5.15.56
• 5.15.57
• 5.15.58
• 5.15.59
• 5.15.60
• 5.15.61
• 5.15.62
• 5.15.63
• 5.15.64
• 5.15.65
• 5.15.66
• 5.15.67
• 5.15.68
• 5.15.69
• 5.15.70
• 5.15.71
• 5.15.72
• 5.15.73
• 5.15.74
• 5.15.75
• 5.15.76
• 5.15.77
• 5.15.78
• 5.15.79
• 5.15.80
• 5.15.81
• 5.15.82
• 5.15.83
• 5.15.84
• 5.15.85
• 5.15.86
• 5.15.87
• 5.15.88
• 5.15.89
• 5.15.90
• 5.15.91
• 5.15.92
• 5.15.93
• 5.15.94
• 5.15.95
• 5.15.96
• 5.15.97
• 5.15.98
• 5.15.99
• 6.1.0
• 6.1.1
• 6.1.2
• 6.1.3
• 6.1.4
• 6.1.5
• 6.1.6
• 6.1.7
• 6.1.8
• 6.1.9
• 6.1.10
• 6.1.11
• 6.1.12
• 6.1.13
• 6.1.14
• 6.1.15
• 6.1.16
• 6.1.17
• 6.2.0
• 6.2.1
• 6.2.2
• 6.2.3
• 6.2.4

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.0
VulDB Meta Temp Score: 4.9

VulDB Base Score: 4.6
VulDB Temp Score: 4.4
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 5.5
NVD Vector: 🔒

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Privilege escalation
CWE: Unknown
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Nessus ID: 276910
Nessus Name: SUSE SLES12 Security Update : kernel (SUSE-SU-2025:4189-1)

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 5.4.235/5.10.173/5.15.100/6.1.18/6.2.5
Patch: aba298b35619213ca787d08d472049627d8cd012/da26369377f0b671c14692e2d65ceb38131053e1/dcdddb5f490890d058ea1f194d661219e92fe88d/e11e4d524eba2d3c8fdf897d7ce3853f7573bae9/aa75d826c221e8d48607aef33836cf872a159cf1/4cc59f386991ec9374cb4bc83dbe1c0b5a95033f

Timelineinfo

10/01/2025 Advisory disclosed
10/01/2025 +0 days CVE reserved
10/01/2025 +0 days VulDB entry created
01/21/2026 +112 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2023-53477 (🔒)
GCVE (CVE): GCVE-0-2023-53477
GCVE (VulDB): GCVE-100-326604
CERT Bund: WID-SEC-2025-2187 - Linux Kernel: Mehrere Schwachstellen erm&ouml;glichen Denial of Service

Entryinfo

Created: 10/01/2025 15:07
Updated: 01/21/2026 01:53
Changes: 10/01/2025 15:07 (59), 11/24/2025 06:28 (7), 11/27/2025 21:01 (2), 01/21/2026 01:53 (12)
Complete: 🔍
Cache ID: 216::103

Once again VulDB remains the best source for vulnerability data.

Discussion

Are you interested in using VulDB?

Download the whitepaper to learn more about our service!