---
id: CVE-2026-10634
title: >-
  Zephyr's native TCP stack iterates the global connection list in
  net_tcp_foreach() (subsys/net/ip/tcp.c) using the
  SYS_SLIST_FOR_EACH_CONTAINER_SAFE macro, which caches a pointer to the next
  list node
summary: >-
  Zephyr's native TCP stack iterates the global connection list in
  net_tcp_foreach() (subsys/net/ip/tcp.c) using the
  SYS_SLIST_FOR_EACH_CONTAINER_SAFE macro, which caches a pointer to the next
  list node. Prior to this fix the function rele…
severity: medium
cvss: 4.8
cvssVector: 'CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-416
vendor: zephyrproject
product: zephyr
affected:
  - 'zephyr >= 2.5.0, < 4.5.0'
patched:
  - zephyr 4.5.0
published: '2026-06-15'
updated: '2026-08-06'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-10634'
references:
  - url: >-
      https://github.com/zephyrproject-rtos/zephyr/commit/cd85e0e890ab89815c4cbc0a8fbc03a3efa84dc2
    label: vulnerabilities@zephyrproject.org
  - url: >-
      https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-6c57-xfhw-j26x
    label: vulnerabilities@zephyrproject.org
tags:
  - nvd
epss: 0.00274
epssPercentile: 0.17667
ingestedAt: '2026-08-07T06:11:51.861Z'
---

## Overview

Zephyr's native TCP stack iterates the global connection list in net_tcp_foreach() (subsys/net/ip/tcp.c) using the SYS_SLIST_FOR_EACH_CONTAINER_SAFE macro, which caches a pointer to the next list node. Prior to this fix the function released tcp_lock while invoking the per-connection callback and re-acquired it afterwards.

During that window a concurrent tcp_conn_release(), running on the dedicated TCP work-queue thread when a connection's reference count drops to zero (e.g. a remote peer closing or resetting the connection), can remove and k_mem_slab_free() the cached next connection. When the iterator advances it dereferences the freed (and possibly reallocated) slab memory — a use-after-free that can crash the system (denial of service) and, if the slot has been reused, cause the callback to operate on an attacker-influenced object (potential information disclosure or further fault).

net_tcp_foreach() is reached in production via the net conn network shell command and via net_tcp_close_all_for_iface() on interface-down; the freeing side is driven by ordinary TCP traffic.

The fix moves the connection/context teardown in tcp_conn_release() inside the tcp_lock critical section and keeps tcp_lock held across the callback in net_tcp_foreach(). The defect was introduced with the modern (TCP2) stack in 2020 and affects releases up to and including v4.4.0.

## Affected

- `zephyr >= 2.5.0, < 4.5.0`

## Remediation

Upgrade past the affected range:

- `zephyr 4.5.0`