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CVE-2026-5590 zephyrproject-rtos CVE debrief

A race condition during TCP connection teardown can cause tcp_recv() to operate on a connection that has already been released. If tcp_conn_search() returns NULL while processing a SYN packet, a NULL pointer derived from stale context data is passed to tcp_backlog_is_full() and dereferenced without validation, leading to a crash. This vulnerability affects users of the Zephyr project, particularly those using versions up to 4.3.0. The Common Vulnerability Scoring System (CVSS) score for this vulnerability is 6.4, indicating a medium severity.

Vendor
zephyrproject-rtos
Product
Zephyr
CVSS
MEDIUM 6.4
CISA KEV
Not listed in stored evidence
Original CVE published
2026-04-05
Original CVE updated
2026-07-24
Advisory published
2026-04-05
Advisory updated
2026-07-24

Who should care

Users of Zephyr project Zephyr versions up to 4.3.0 should be aware of this vulnerability and take steps to mitigate it. This includes reviewing and updating inventory of affected systems, monitoring for potential exploitation attempts, and applying patches from the vendor.

Technical summary

The vulnerability is caused by a race condition during TCP connection teardown. When tcp_conn_search() returns NULL while processing a SYN packet, a NULL pointer derived from stale context data is passed to tcp_backlog_is_full() and dereferenced without validation, leading to a crash. The vulnerability affects the Zephyr project, specifically versions up to 4.3.0. Users of these versions should be aware of this vulnerability and take steps to mitigate it.

Defensive priority

Medium priority should be given to patching this vulnerability, as it can cause a crash and potentially be used by attackers.

Recommended defensive actions

  • Apply the patch from the vendor
  • Review and update inventory of affected systems
  • Monitor for potential exploitation attempts
  • Review compensating controls for exposed systems while remediation is scheduled and verified
  • Check relevant monitoring, detection, and logs for exposed assets that need extra review
  • Track exceptions, retest remediated assets, and close the item only after evidence is documented
  • Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record was published on 2026-04-05T04:16:16.370Z and was last modified on 2026-07-08T13:38:21.667Z. The NVD entry is currently Analyzed. This information is based on the provided source corpus. Further verification is recommended to ensure accuracy.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-5590 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-5590

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-5590 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-5590

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.