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CVE-2026-98438

mptcp: options: fix uninit-value in mptcp_write_data_fin

CVSS score

—

EPSS probability

—

Risk score

—

Published

15 h ago

Patch status has not yet been verified

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Vulnerability description

CVE AI research

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DayBreach AI Explanation

Verified against sources

CVE-2026-98438 Linux Kernel MPTCP Vulnerability

Sources read

1

Source agreement

Tam uyum

Evidence confidence

%55

Short explanation

An uninit-value vulnerability in mptcp_write_data_fin within the Linux kernel MPTCP subsystem has been resolved [S0]. When sending a DATA_FIN without data and if the checksum has been negotiated, the initial csum data needs to be reset [S0].

Why does it matter?

This vulnerability affects the MPTCP component of the Linux kernel and can lead to uninit-value issues during packet transmission [S0]. The patch status remains unverified in official sources [S0].

What should be done?

  • Follow vendor advisories and security updates [S0]
  • Review the corresponding stable kernel patch references [S1]
Chain of evidence and sources2 verified claims

Linux çekirdeğindeki mptcp_write_data_fin içerisinde bir uninit-value zafiyeti çözülmüştür [S0].

Sorun, ext_copy yapısının varsayılan olarak sıfırlanmamasından kaynaklanmaktadır [S0].

Show the technical text from the sources

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.

Explanation produced with the local gemini-flash-lite-latest model. Numerical metrics and the KEV, patch and exploit statuses are not determined by AI.

IMPACT: Affected Products and Software

Affected Products

The following products are affected by CVE-2026-98438 vulnerability. Where our threat engine knows the exact affected versions, they are listed below.

IDVENDORPRODUCTACTION
1linuxLinux View
2linuxLinux View
Total affected vendors: 1|Products: 2

RED HAT CSAF/VEX: Product Impact Check

Red Hat has not yet published a CSAF/VEX impact record for this CVE. This does not mean “not affected”.

SCORING: CVSS from Multiple Sources

CVSS Scores

The Common Vulnerability Scoring System is a standardised framework for assessing the severity of vulnerabilities in software and systems. We collect and display CVSS scores from several sources for each CVE.

SCOREVERSIONSEVERITYVECTORSOURCE
The sources have not yet published a verified CVSS metric.

Patch and Remediation Guide

Solution & Remediation Advisory

Patch status unknown

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Confirm the affected product and version against the source evidence above.
Restrict access to internet-facing services and apply network segmentation.
Until a patch is confirmed, follow the vendor advisory; do not read an unknown status as “no patch”.
Monitor server logs and network endpoints for signs of anomalous execution.

Public exploit and active exploitation status

Verified exploit intelligence

No verified public PoC, exploit repository or Metasploit module has been found for this CVE yet.

Weakness Classification and Attack Patterns (CWE & CAPEC)

CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorises the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-98438 is associated with the following CWEs:

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-98438 weaknesses.

Official Sources and Advisories

Yama durumu bilinmiyor

İncelenen resmî kaynaklarda yama durumu doğrulanamadı. Bu sonuç “yama yok” anlamına gelmez.

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