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CVE-2026-14368: bounds in zephyrproject zephyr

0
Medium
VulnerabilityCVE-2026-14368cvecve-2026-14368
Published: 08/31/2026 (08/31/2026, 18:45:07 UTC)
Source: CVE Database V5
Vendor/Project: zephyrproject
Product: zephyr

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.

CVSS v3.1

Score 5.4medium

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
Low
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L

Affected software

GitHub Actionsmore threats →cve
zephyr
pkg:github/zephyr
Affected versions
>=3.2.0 <4.4.2

Run on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.

Technical Details

Data Version
5.2
Assigner Short Name
zephyr
Date Reserved
2026-07-01T19:30:21.245Z
Cvss Version
3.1
State
PUBLISHED
Remediation Level
null

Threat ID: 6a95cd85acd9273b49762f7d

Added to database: 08/31/2026, 18:52:53 UTC

Last updated: 08/31/2026, 19:37:51 UTC

Views: 5

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