CVE-2026-98438
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 occupie…
Overview
CVE-2026-98438 is a known-severity vulnerability. It was published on October 18, 2026.
Technical 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.
Remediation
Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
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Frequently asked questions
What is CVE-2026-98438?
CVE-2026-98438 is a known-severity vulnerability. It was published on October 18, 2026.
How severe is CVE-2026-98438?
CVSS score information is not yet available for this vulnerability. Check back as the CVE record is updated by NVD analysts.
How do I fix or remediate CVE-2026-98438?
Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-98438?
CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-98438 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.