5.4
MEDIUM CVSS 3.1
CVE-2026-14368
Off-by-one out-of-bounds NUL write in Zephyr LwM2M JSON string parser
Description

The LwM2M JSON content formatter's get_string() in subsys/net/lib/lwm2m/lwm2m_rw_json.c copies a parsed JSON string into a caller-supplied buffer and NUL-terminates it. The length guard used if (string_length > buflen), which accepts a string whose length is exactly buflen. After memcpy() fills the whole buffer, buf[string_length] = '\0' then writes one byte past the end of the buffer (CWE-787). The string value and its length are taken directly from the incoming CoAP payload during a LwM2M WRITE: do_write_op_json() parses the payload obtained from coap_packet_get_payload(), and get_string() is invoked from lwm2m_write_handler() (engine_get_string() in subsys/net/lib/lwm2m/lwm2m_message_handling.c) for a LWM2M_RES_TYPE_STRING resource. The destination buf/buflen is either the resource instance's fixed data buffer (res_inst->data_ptr/max_data_len) or the engine validation buffer (msg->ctx->validate_buf). A LwM2M server (the client's DTLS peer) can therefore write a string resource with a value whose length equals the target buffer size and force a one-byte overflow. The overflow is a single out-of-bounds write of the constant byte 0x00 immediately past the resource or validation buffer, corrupting the adjacent byte in memory. It is not an information leak and the written value is fixed, so it is not a direct code-execution primitive, but it can corrupt adjacent state (an adjacent resource value, a length/flag field, or a struct field) and cause data corruption or a crash. Triggering the write is deterministic; the resulting impact depends on memory layout. The fix changes the guard to string_length >= buflen, rejecting the exact-length case and aligning the JSON formatter with the other content formatters (lwm2m_rw_plain_text.c, lwm2m_rw_oma_tlv.c, lwm2m_rw_senml_json.c, lwm2m_rw_cbor.c, lwm2m_rw_senml_cbor.c), which already used the correct boundary check.

INFO

Published Date :

Aug. 31, 2026, 7:16 p.m.

Last Modified :

Aug. 31, 2026, 7:16 p.m.

Remotely Exploit :

No
Affected Products

The following products are affected by CVE-2026-14368 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID Vendor Product Action
1 Zephyrproject zephyr
2 Zephyrproject zephyr
CVSS Scores
The Common Vulnerability Scoring System is a standardized framework for assessing the severity of vulnerabilities in software and systems. We collect and displays CVSS scores from various sources for each CVE.
Score Version Severity Vector Exploitability Score Impact Score Source
CVSS 3.1 MEDIUM e2e69745-5e70-4e92-8431-deb5529a81ad
CVSS 3.1 MEDIUM [email protected]
Solution
Fix buffer overflow by adjusting string length validation.
  • Update the string length guard condition.
  • Reject exact length strings.
  • Align JSON formatter checks.
  • Apply the provided code fix.
References to Advisories, Solutions, and Tools

Here, you will find a curated list of external links that provide in-depth information, practical solutions, and valuable tools related to CVE-2026-14368.

URL Resource
https://github.com/zephyrproject-rtos/zephyr/commit/ba38f4b94337cc2c2446277ac181bdb5fec8f2b2
https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-vg53-h6qq-xx7h
CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-14368 is associated with the following CWEs:

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-14368 weaknesses.

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2026-14368 vulnerability anywhere in the article.

The following table lists the changes that have been made to the CVE-2026-14368 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

  • New CVE Received by [email protected]

    Aug. 31, 2026

    Action Type Old Value New Value
    Added Description The LwM2M JSON content formatter's get_string() in subsys/net/lib/lwm2m/lwm2m_rw_json.c copies a parsed JSON string into a caller-supplied buffer and NUL-terminates it. The length guard used if (string_length > buflen), which accepts a string whose length is exactly buflen. After memcpy() fills the whole buffer, buf[string_length] = '\0' then writes one byte past the end of the buffer (CWE-787). The string value and its length are taken directly from the incoming CoAP payload during a LwM2M WRITE: do_write_op_json() parses the payload obtained from coap_packet_get_payload(), and get_string() is invoked from lwm2m_write_handler() (engine_get_string() in subsys/net/lib/lwm2m/lwm2m_message_handling.c) for a LWM2M_RES_TYPE_STRING resource. The destination buf/buflen is either the resource instance's fixed data buffer (res_inst->data_ptr/max_data_len) or the engine validation buffer (msg->ctx->validate_buf). A LwM2M server (the client's DTLS peer) can therefore write a string resource with a value whose length equals the target buffer size and force a one-byte overflow. The overflow is a single out-of-bounds write of the constant byte 0x00 immediately past the resource or validation buffer, corrupting the adjacent byte in memory. It is not an information leak and the written value is fixed, so it is not a direct code-execution primitive, but it can corrupt adjacent state (an adjacent resource value, a length/flag field, or a struct field) and cause data corruption or a crash. Triggering the write is deterministic; the resulting impact depends on memory layout. The fix changes the guard to string_length >= buflen, rejecting the exact-length case and aligning the JSON formatter with the other content formatters (lwm2m_rw_plain_text.c, lwm2m_rw_oma_tlv.c, lwm2m_rw_senml_json.c, lwm2m_rw_cbor.c, lwm2m_rw_senml_cbor.c), which already used the correct boundary check.
    Added CVSS V3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L
    Added CWE CWE-787
    Added CWE CWE-193
    Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/14xxx/CVE-2026-14368.json">CVE-2026-14368</a>
    Added Reference https://github.com/zephyrproject-rtos/zephyr/commit/ba38f4b94337cc2c2446277ac181bdb5fec8f2b2
    Added Reference https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-vg53-h6qq-xx7h
EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.