Linux Kernel up to 6.18.54/7.2.8 macsec rtmsg_ifinfo_build_skb uninitialized variable

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.
4.0	$0-$5k	1.65-

Summaryinfo

A vulnerability classified as problematic was found in Linux Kernel up to 6.18.54/7.2.8. Affected by this issue is the function rtmsg_ifinfo_build_skb of the component macsec. The manipulation results in uninitialized variable. This vulnerability is reported as CVE-2026-98929. The attack requires a local approach. No exploit exists. Upgrading the affected component is advised.

Detailsinfo

A vulnerability, which was classified as problematic, was found in Linux Kernel up to 6.18.54/7.2.8. Affected is the function rtmsg_ifinfo_build_skb of the component macsec. The manipulation with an unknown input leads to a uninitialized variable vulnerability. CWE is classifying the issue as CWE-457. The code uses a variable that has not been initialized, leading to unpredictable or unintended results. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: macsec: initialize SecY before registering the netdevice Creating a MACsec device with MAC offload over an LRO-capable lower device triggers a warning in rtmsg_ifinfo_build_skb() when IPv4 forwarding is enabled by default. register_netdevice() invokes inetdev_init(), which disables LRO and emits a NETDEV_FEAT_CHANGE notification. This reaches macsec_fill_info() before macsec_add_dev() initializes the SecY. key_len is still zero, so macsec_fill_info() returns -EMSGSIZE and trips the WARN_ON in rtmsg_ifinfo_build_skb(), even though the skb has enough space. Even without the warning, notifications during registration can report uninitialized SecY attributes, including the SCI. This ordering has existed since the driver was introduced. Initialize the SecY and apply the new-link attributes before registration. Move MAC address inheritance into macsec_newlink() so the SCI can also be initialized before registration-time notifications report it. Move the per-CPU statistics and metadata destination allocation into ndo_init(), and release partial allocations on failure.

The advisory is shared for download at git.kernel.org. This vulnerability is traded as CVE-2026-98929 since 09/25/2026. The exploitability is told to be easy. The attack needs to be approached locally. Additional levels of successful authentication are required for exploitation. There are known technical details, but no exploit is available.

Upgrading to version 6.18.55 or 7.2.9 eliminates this vulnerability. Applying the patch 2b42adf3b8ee9a0e1d2629aca3c5a02a1c438066/b07bea42bf590edb0fd507ab25622a74af09548b/c2de369c5c5b8599ca10fd5ca8d11fcd845c1331 is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.18.6
• 6.18.7
• 6.18.8
• 6.18.9
• 6.18.10
• 6.18.11
• 6.18.12
• 6.18.13
• 6.18.14
• 6.18.15
• 6.18.16
• 6.18.17
• 6.18.18
• 6.18.19
• 6.18.20
• 6.18.21
• 6.18.22
• 6.18.23
• 6.18.24
• 6.18.25
• 6.18.26
• 6.18.27
• 6.18.28
• 6.18.29
• 6.18.30
• 6.18.31
• 6.18.32
• 6.18.33
• 6.18.34
• 6.18.35
• 6.18.36
• 6.18.37
• 6.18.38
• 6.18.39
• 6.18.40
• 6.18.41
• 6.18.42
• 6.18.43
• 6.18.44
• 6.18.45
• 6.18.46
• 6.18.47
• 6.18.48
• 6.18.49
• 6.18.50
• 6.18.51
• 6.18.52
• 6.18.53
• 6.18.54
• 7.2.0
• 7.2.1
• 7.2.2
• 7.2.3
• 7.2.4
• 7.2.5
• 7.2.6
• 7.2.7
• 7.2.8

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: 4.2
VulDB Meta Temp Score: 4.0

VulDB Base Score: 4.2
VulDB Temp Score: 4.0
VulDB Vector: 🔒
VulDB Reliability: 🔍

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: Uninitialized variable
CWE: CWE-457 / CWE-453
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: No

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.18.55/7.2.9
Patch: 2b42adf3b8ee9a0e1d2629aca3c5a02a1c438066/b07bea42bf590edb0fd507ab25622a74af09548b/c2de369c5c5b8599ca10fd5ca8d11fcd845c1331

Timelineinfo

09/25/2026 CVE reserved
10/23/2026 +28 days Advisory disclosed
10/23/2026 +0 days VulDB entry created
10/23/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-98929 (🔒)
GCVE (CVE): GCVE-0-2026-98929
GCVE (VulDB): GCVE-100-425712

Entryinfo

Created: 10/23/2026 14:46
Changes: 10/23/2026 14:46 (59)
Complete: 🔍
Cache ID: 216::103

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