NVD / CVE Program· CNA zephyr

CVE-2026-10634: Use-after-free in Zephyr native TCP `net_tcp_foreach()` due to dropping `tcp_lock` during the callback

MediumCVSS 5.3 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 21/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.27% (FIRST EPSS).
Someone on the same network segment can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
Fixed version: zephyrproject zephyr 4.3.1, 4.4.1.

Low priority for now. Upgrade to zephyrproject zephyr 4.3.1, 4.4.1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

Published: Jun 15, 2026
Updated: Nov 5, 2026
EPSS: 0.2% · 20th percentile
CWE: CWE-416

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 21 / 40 · 5.3 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.2%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: 5.3
CNA · zephyr: 4.8; 0.5 point gap

CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
zephyrproject	zephyr	cpe:2.3:o:zephyrproject:zephyr

Versions reported by the vendor

Affected version ranges reported by the assigning authority (zephyr). Independent of NVD's CPE analysis and usually ahead of it.

zephyrproject zephyr
- 3.6.0 and later · before 4.3.1affected · semver
- 4.4.0 and later · before 4.4.1affected · semver

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

zephyrproject zephyr2.5.0 and later · up to 3.7.2 inclusive
zephyrproject zephyr4.0.0 and later · before 4.3.1
zephyrproject zephyr4.4.0 and later · before 4.4.1

Same product

zephyrproject: all records

Other highest-scoring records for the same primary product.

CVE-2023-4260Potential off-by-one buffer overflow vulnerability in the Zephyr FS subsystem
40Plan
CVE-2021-3625Buffer overflow in Zephyr USB DFU DNLOAD
40Plan
CVE-2020-10071Insufficient publish message length validation in MQTT
40Plan

Published before and after this one in the same product

← EarlierCVE-2026-5067Jun 9, 2026 · Out-of-bounds read/write in HTTP WebSocket upgrade via non-null-terminated Sec-WebSocket-Key
39Monitor
← EarlierCVE-2026-5068Jun 9, 2026 · bt: l2cap le coc: remote oob write via seg counter stored in net_buf user_data
35Monitor
Later →CVE-2026-10635Jun 16, 2026 · Dangling memory-domain pointer (use-after-free) in Xtensa MMU page-table code on memory-domain de-init
25Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
zephyrproject zephyr	4.3.1	Vendor (CNA)
zephyrproject zephyr	4.4.1	Vendor (CNA)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

zephyrproject-rtos/zephyrcommit cd85e0e

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

CVE-2026-1236660 days apartUse-after-free freeing an armed dynamically-allocated k_timer in Zephyr userspace object disposal
35Monitor
CVE-2026-85035141 days apartUse-after-free via dynamically allocated message queue retained by the CAN RX filter
35Monitor
CVE-2026-1066727 days apartSMP use-after-free in Zephyr `CONFIG_USERSPACE` dynamic kernel-object tracking, reachable from unprivileged user threads
31Monitor
CVE-2026-79979130 days apartStale TLB entries after demand-paging page-out let arm64 user threads access reused physical frames
31Monitor
CVE-2026-106381 days apartUse-after-free in Zephyr ICMPv6 RX path when updating statistics after sending an echo reply or error
30Monitor
CVE-2026-1068546 days apartUse-after-free of GATT subscribe params in Bluetooth host CCC-write response handler
30Monitor

Not on record for this CVE: EPSS history · researcher credit · public bounty program.

Technical details

Attack conditions

Someone on the same network segment can trigger it.
No account or password is required.
No user action is required.
Special conditions such as timing or configuration are required.

If successful

Confidentiality: none
Integrity: none
Availability: high · the service can be disrupted

Attack vector: Adjacent
Attack complexity: High
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: None
Integrity impact: None
Availability impact: High

Weakness class (CWE)

CWE-416 · Use After Free

CVSS vector

CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Root cause

After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.

The bug in code

The whole CWE-416 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1free(dev->buf);
2/* ... another thread is still running ... */
3process(dev->buf);

Fixed

1lock(&dev->lock);
2free(dev->buf);
3dev->buf = NULL;
4unlock(&dev->lock);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log (1)

Fix✗ → ✓Sep 28, 2026, 10:08 PM UTC

For records you follow, these changes also arrive as notifications. →

References

github.com/zephyrproject-rtos/zephyr/commit/cd85e0e890ab89815c4cbc0a8fbc03a3efa84dc2

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records