CVE-2026-23321

Local availability loss via MPTCP endpoint misaccounting

Published Mar 25, 2026 · Updated Mar 25, 2026

Incorrect endpoint accounting in the Linux kernel MPTCP path manager allows local users to disrupt availability during endpoint removal. When signaling clears an endpoint's availability bit without creating a subflow, mptcp_pm_create_subflow_or_signal_addr leaves local_addr_used at zero, and later removal reaches an invalid accounting assumption. The trigger requires local access, a zero subflow limit, a signal-and-subflow endpoint, a connection from another address, and endpoint removal.

CVSS severity5.5
Medium
EPSS probability0.12%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Incorrect endpoint accounting in the Linux kernel MPTCP path manager allows local users to disrupt availability during endpoint removal. When signaling clears an endpoint's availability bit without creating a subflow, mptcp_pm_create_subflow_or_signal_addr leaves local_addr_used at zero, and later removal reaches an invalid accounting assumption. The trigger requires local access, a zero subflow limit, a signal-and-subflow endpoint, a connection from another address, and endpoint removal.

The record

CVE
CVE-2026-23321
Published
Mar 25, 2026
Updated
Mar 25, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
Unavailable
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 25, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0f21cc29bc13e86512621727a4388c8a7ad2716b
  2. Affected versionversion=6.11
  3. Affected versionversion=64815ba15880ce5f99df075fa4104fef170ac7e5 <05799c2f1ca5eb13d65764dda688d02021b65e06
  4. Affected versionversion=85df533a787bf07bf4367ce2a02b822ff1fba1a3 <198824ccfa64ffebd918bf99c939bd8170a4a4d8
  5. Affected versionversion=85df533a787bf07bf4367ce2a02b822ff1fba1a3 <579a752464a64cb5f9139102f0e6b90a1f595ceb
  6. Affected versionversion=85df533a787bf07bf4367ce2a02b822ff1fba1a3 <67f34ab318807989b57dfdb0f79e2d4e57018290
  7. Affected versionversion=85df533a787bf07bf4367ce2a02b822ff1fba1a3 <a64aa7db39392add5be09dffaedbf1f0ce5554df
  8. Affected versionversion=d93cf38fad9f66397093432b8917971a92ee0146 <c5c877e140e5f46023a74a51e577ce5edd0a4be7

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=0f21cc29bc13e86512621727a4388c8a7ad2716b; version=6.11; version=64815ba15880ce5f99df075fa4104fef170ac7e5 <05799c2f1ca5eb13d65764dda688d02021b65e06; version=85df533a787bf07bf4367ce2a02b822ff1fba1a3 <198824ccfa64ffebd918bf99c939bd8170a4a4d8; version=85df533a787bf07bf4367ce2a02b822ff1fba1a3 <579a752464a64cb5f9139102f0e6b90a1f595ceb; version=85df533a787bf07bf4367ce2a02b822ff1fba1a3 <67f34ab318807989b57dfdb0f79e2d4e57018290; version=85df533a787bf07bf4367ce2a02b822ff1fba1a3 <a64aa7db39392add5be09dffaedbf1f0ce5554df; version=d93cf38fad9f66397093432b8917971a92ee0146 <c5c877e140e5f46023a74a51e577ce5edd0a4be7

Published CVSS scores

5.5Canonical UbuntuCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo