CVE-2026-5590Network attack vector

Device crash via TCP teardown race

Published Apr 5, 2026 · Updated Apr 5, 2026

NULL pointer dereference in Zephyr RTOS 4.3 and earlier allows remote authenticated users to crash devices during TCP SYN processing. During a teardown race, tcp_recv() retains stale connection context after tcp_conn_search() returns NULL and passes the resulting NULL pointer to tcp_backlog_is_full() without validation. Exploitation requires low privileges, network reachability, a concurrent connection release, and a newly processed SYN; success terminates the affected device software.

CVSS severity6.4
Medium
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in Zephyr RTOS 4.3 and earlier allows remote authenticated users to crash devices during TCP SYN processing. During a teardown race, tcp_recv() retains stale connection context after tcp_conn_search() returns NULL and passes the resulting NULL pointer to tcp_backlog_is_full() without validation. Exploitation requires low privileges, network reachability, a concurrent connection release, and a newly processed SYN; success terminates the affected device software.

The record

CVE
CVE-2026-5590
Published
Apr 5, 2026
Updated
Apr 5, 2026
Vendor
Zephyr Project
Product
Zephyr RTOS
Classifications
CWE-476, T1499
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 5, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=* <=4.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Zephyr Project · Zephyr RTOSversion=* <=4.3

Published CVSS scores

6.4Zephyr ProjectCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
5.3NIST NVDCVSS:3.1/AV:N/AC:H/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)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499Endpoint Denial of Service

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

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Your stack

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