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CVE-2026-14368— Off-by-one out-of-bounds NUL write in Zephyr LwM2M JSON string parser

Quick assessment

Affected
zephyrproject zephyr
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

zephyrproject Zephyr是zephyrproject组织开源的一款面向物联网设备的实时操作系统。 zephyrproject Zephyr 3.2.0至4.4.2之前版本存在安全漏洞，该漏洞源于subsys/net/lib/lwm2m/lwm2m_rw_json.c文件中的get_string()函数在复制JSON字符串时长度检查不当，当字符串长度等于缓冲区大小时，NUL终止符会写入缓冲区末尾之外的一个字节，可能导致越界写入并破坏相邻内存，造成数据损坏或崩溃。

CVSS 5.4 · Medium EPSS 0.23% · P12

Affected Version Matrix 1

VendorProduct Version RangeStatus
zephyrproject zephyr 3.2.0< 4.4.2 affected
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I. Basic Information for CVE-2026-14368

Vulnerability Information
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Vulnerability Title
Off-by-one out-of-bounds NUL write in Zephyr LwM2M JSON string parser
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存写
Source: CVE Program / CVE List V5
Vulnerability Title
zephyrproject Zephyr 数字错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
zephyrproject Zephyr是zephyrproject组织开源的一款面向物联网设备的实时操作系统。 zephyrproject Zephyr 3.2.0至4.4.2之前版本存在安全漏洞，该漏洞源于subsys/net/lib/lwm2m/lwm2m_rw_json.c文件中的get_string()函数在复制JSON字符串时长度检查不当，当字符串长度等于缓冲区大小时，NUL终止符会写入缓冲区末尾之外的一个字节，可能导致越界写入并破坏相邻内存，造成数据损坏或崩溃。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
zephyrproject zephyr 3.2.0 ~ 4.4.2 -

II. Public POCs for CVE-2026-14368

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III. Intelligence Information for CVE-2026-14368

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Patches & Fixes for CVE-2026-14368 (1)

Vendor Advisories for CVE-2026-14368 (1)

Same Patch Batch · zephyrproject · 2026-08-31 · 5 CVEs total

CVE-2026-14696 6.5 MEDIUM Ethernet bridge RX packet leak enables denial of service via RX buffer-pool exhaustion
CVE-2026-14697 6.5 MEDIUM IPv6 Neighbor Solicitation packet leak causes TX pool exhaustion denial of service
CVE-2026-14366 6.4 MEDIUM SiWx91x WiFi driver double-unref / use-after-free of caller-owned TX net_pkt
CVE-2026-14367 3.1 LOW I3C IBI work-node free-list data race between ISR and workqueue thread

IV. Related Vulnerabilities

Same product: zephyr
Same vendor: zephyrproject
Same weakness: CWE-787

V. Comments for CVE-2026-14368

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