CVE-2026-98438
Received Received - Intake

Uninitialized Value in Linux Kernel MPTCP Options

Publication date: 2026-10-18

Last updated on: 2026-10-18

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: mptcp: options: fix uninit-value in mptcp_write_data_fin When sending a DATA_FIN without data, and because the DATA_FIN occupies 1 octet of the connection-level sequence space [1], it is then required to add a DSS mapping with specific values. If the checksum has been negotiated, it also needs to be computed, and included in the outgoing packet, and thus the initial csum data needs to be reset to 0 as well. This is no longer the case since commit cfcceb7a39fc ("tcp: shrink per-packet memset in __tcp_transmit_skb()"), because the whole ext_copy structure is no longer zeroed by default. This seems to be the only case where use_map is changed and set afterwards, so initialising the csum field only in this case, along with other fields for this specific case.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published
2026-10-18
Last Modified
2026-10-18
Generated
2026-10-18
AI Q&A
2026-10-18
EPSS Evaluated
N/A
NVD
CVE-2026-98438
EUVD
EUVD-2026-103677

Affected Vendors & Products

Showing 3 associated CPEs
Vendor Product Version / Range
Linux Linux cfcceb7a39fc10a6f896af8229bf81d96acb22cc
Linux Linux cfcceb7a39fc10a6f896af8229bf81d96acb22cc
Linux Linux 7.1

Helpful Resources

Exploitability

CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-UNKNOWN

Attack-Flow Graph

AI Quick Actions

Instant insights powered by AI
Executive Summary

This vulnerability in the Linux kernel involves improper handling of DATA_FIN packets in the Multipath TCP (MPTCP) subsystem. When sending a DATA_FIN without data, the system fails to properly initialize checksum fields due to a change in how packet data is zeroed. This can lead to uninitialized memory being used in network packets.

Detection Guidance

This vulnerability is specific to the Linux kernel's MPTCP implementation and requires kernel-level inspection. Detection involves checking kernel logs for MPTCP-related errors or monitoring network traffic for malformed MPTCP packets. Commands like dmesg, journalctl -k, or tcpdump with MPTCP filters may help identify issues. No direct user-space commands are provided in the context.

Impact Analysis

This vulnerability could allow an attacker to cause a denial of service or potentially execute arbitrary code on affected systems. It may lead to network packet corruption or crashes in systems using MPTCP with checksum negotiation enabled.

Mitigation Strategies

Apply the latest Linux kernel patches to address the uninit-value issue in mptcp_write_data_fin. Ensure your system is updated to a version where the fix in commit cfcceb7a39fc is included.

Chat Assistant

Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-98438. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70

EPSS Chart