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NVD / CVE Program· CNA zephyr

CVE-2026-5066: net: sockets: tls: Potential out-of-bounds write/read in socket_op_vtable::connect function

Noroxi assessment

Priority: Monitor (action score 35/100)

  • 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: 0.32% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: zephyrproject-rtos Zephyr 3.7.2, 4.2.2, 4.3.1.
  • Severity is disputed: the assigning authority (CNA) scores it 6.3, NVD 8.8.

Low priority for now. Upgrade to zephyrproject-rtos Zephyr 3.7.2, 4.2.2, 4.3.1 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

A potential out-of-bounds write/read exists in the TLS socket connect path of the network sockets subsystem (subsys/net/lib/sockets/sockets_tls.c). When the TLS session cache is enabled, tls_session_store() and tls_session_restore() memcpy the caller-supplied address into a fixed-size buffer using the caller-controlled addrlen value without validating it against the destination size. struct net_sockaddr is an opaque type, so an application can pass an addrlen larger than sizeof(struct net_sockaddr) (for example 128 bytes into a 24-byte stack buffer), causing the memcpy to read and write past the end of the address memory used by the TLS session cache. This out-of-bounds write can lead to a crash and denial of service, and potentially to arbitrary code execution.

HighCVSS 8.8 · v3.1—No exploit Fix available
Published
Jun 4, 2026
Updated
Oct 15, 2026
EPSS
0.3% · 25th percentile

Report tools

JSON

Action score

35

Monitor

Low priority for now.

CVSS
35 / 40 · 8.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

CISA SSVC decision

Exploitation
proof of concept
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
8.8
CNA · zephyr
6.3
2.5 point gap

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

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

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

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When you'll hear from us

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  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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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.

VendorProduct
zephyrprojectzephyr

Affected versions

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

  • zephyrproject zephyrup to 4.3.0 inclusive

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-rtos Zephyr

    • before 3.7.2affected · git
    • 4.0.0 and later · before 4.2.2affected · git
    • 4.3.0 and later · before 4.3.1affected · git

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-2026-5071May 30, 2026 · can: Local Denial of Service via SocketCAN Send
    31Monitor
  • ← EarlierCVE-2026-5589Jun 4, 2026 · Out-of-bounds write caused by an integer underflow in the Bluetooth Mesh subsystem.
    25Monitor
  • Later →CVE-2026-5067Jun 9, 2026 · Out-of-bounds read/write in HTTP WebSocket upgrade via non-null-terminated Sec-WebSocket-Key
    39Monitor

Remediation

Which version to upgrade to

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

Product / packageFixed versionSource
zephyrproject-rtos Zephyr3.7.2Vendor (CNA)
zephyrproject-rtos Zephyr4.2.2Vendor (CNA)
zephyrproject-rtos Zephyr4.3.1Vendor (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.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

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

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

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

  • CVE-2026-1321482 days apartStack buffer overflow in OCPP GetConfiguration key parsing
    39Monitor
  • CVE-2026-167891 days apartdns: memory‑safety issue in the DNS name parser
    39Monitor
  • CVE-2026-82391159 days apartOut-of-bounds write in Zephyr HTTP/2 server static-filesystem handler via corrupted receive-buffer length
    36Monitor
  • CVE-2026-50685 days apartbt: l2cap le coc: remote oob write via seg counter stored in net_buf user_data
    35Monitor
  • CVE-2026-1252276 days apartStack buffer overflow in Zephyr hl7800 modem driver parsing network-supplied +CGCONTRDP address fields
    35Monitor
  • CVE-2026-76788137 days apartStack out-of-bounds write in the OSDP Control Panel reply parser
    35Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

  • CVE-2026-79977141 days apartWireGuard peer endpoint learned from unauthenticated transport-data messages allows off-path tunnel hijack in Zephyr
    32Monitor
  • CVE-2026-765625 days apartBroken IPv6 Neighbor Discovery input validation allows spoofed RA/NS/NA acceptance in Zephyr net stack
    27Monitor
  • CVE-2026-1373485 days apartZephyr WireGuard mutates peer state before anti-replay check, enabling capture-replay endpoint hijack
    26Monitor
  • CVE-2026-1063612 days apartUse-after-free in Zephyr IPv4 IGMP send path (`igmp_send`)
    14Monitor

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-787 · Out-of-bounds Write

CVSS vector

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

nvd-primary

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✗ → ✓

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