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ZephyrOperating system · Zephyrproject

CVE-2026-10672

CRITICAL · 9.1 CVSS v3.1 Published 2026-07-14
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click 5 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
subsys/net/lib/lwm2m/lwm2m_pull_context.c copied the firmware-update Package URI into a fixed static buffer (context.uri, size CONFIG_LWM2M_SWMGMT_PACKAGE_URI_LEN, default 128) with memcpy(context.uri, uri, LWM2M_PACKAGE_URI_LEN), copying exactly the destination size with no length validation. The Firmware-Update object stores the server-supplied Package URI (/5/0/1) in a 255-byte buffer, so a LwM2M management server (or an on-path attacker on a session lacking strong DTLS) can WRITE a URI of 128-254 characters; only the first 128 bytes are then copied into context.uri with no NUL terminator. That buffer is subsequently consumed as a C string by http_parser_parse_url(context.uri, strlen(context.uri), ...), strlen-based CoAP URI-path/PROXY-URI option appends, and lwm2m_parse_peerinfo(), causing an out-of-bounds read of adjacent static memory. The over-read bytes are appended to outbound CoAP requests (information disclosure of adjacent device memory to the server/proxy) and can crash the device (denial of service). The vulnerable copy was introduced by the pull-context refactor (first released in v3.0.0) and is present through v4.4.0; the default-on CONFIG_LWM2M_FIRMWARE_UPDATE_PULL_SUPPORT path is affected. The fix adds a strlen(uri) >= sizeof(context.uri) check returning -ENOMEM and switches to strcpy(), guaranteeing a bounded, NUL-terminated buffer.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

In Zephyr RTOS LwM2M implementation, lwm2m_pull_context.c copies a server-supplied firmware-update Package URI into a fixed 128-byte buffer via memcpy without validating length. A malicious or compromised LwM2M server can send a URI of 128-254 bytes; only the first 128 bytes are copied with no NUL terminator. Subsequent string operations (strlen, http_parser_parse_url, URI-path appends) read beyond the buffer boundary, causing information disclosure of adjacent device memory to the server and potential device crashes.

MitigationUpdate to Zephyr RTOS v4.4.1 or later which includes the strlen bounds check and proper NUL-terminated string copy; alternatively, disable CONFIG_LWM2M_FIRMWARE_UPDATE_PULL_SUPPORT if firmware pull is not required.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
ZephyrOperating system
Affected:= 3.7.1= 4.2.1= 4.3.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Confirm LwM2M firmware pull is enabled
    Inspect build configuration files (prj.conf, defconfig) or run 'grep -r CONFIG_LWM2M_FIRMWARE_UPDATE_PULL_SUPPORT' in the project build directory. Check for CONFIG_LWM2M_FIRMWARE_UPDATE_PULL_SUPPORT=y
    Affected if CONFIG_LWM2M_FIRMWARE_UPDATE_PULL_SUPPORT is set to y (enabled)
  2. Identify Zephyr RTOS version
    Check the version of Zephyr RTOS used in the firmware build. Look for VERSION or KERNEL_VERSION variables in build logs, or check the 'version' file in the Zephyr SDK installation directory, or inspect the 'west.yml' manifest file for the 'version' tag
    Affected if Version is earlier than v4.4.1 (the fixed release)
  3. Verify device acts as LwM2M client
    Review application code for lwm2m_client_init() or related LwM2M client API calls. Check if the device registers with an LwM2M server (examine network configuration for LwM2M server URI)
    Affected if Device implements an LwM2M client that connects to a remote server
  4. Check if firmware update objects are registered
    Examine application source code for lwm2m_engine_create_obj_inst() calls for /5/0/0 (Firmware Update object) or examine the compiled binary for LwM2M object 5 references
    Affected if Firmware Update object (Object ID 5) is instantiated in the LwM2M client
  5. Inspect buffer configuration in lwm2m_pull_context.c
    If source code is accessible, locate the hardcoded 128-byte buffer (e.g., char uri[128] or #define PACKAGE_URI_LEN 128) used for Package URI in lwm2m_pull_context.c. Verify no bounds checking exists before memcpy
    Affected if A 128-byte fixed buffer is used without length validation prior to memcpy

Device is affected if it uses Zephyr RTOS versions prior to v4.4.1 with CONFIG_LWM2M_FIRMWARE_UPDATE_PULL_SUPPORT enabled and implements the LwM2M client with Firmware Update object, allowing a malicious server to supply an oversized URI that overflows the fixed buffer.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Update to Zephyr RTOS v4.4.1 or later which includes the strlen bounds check and proper NUL-terminated string copy; alternatively, disable CONFIG_LWM2M_FIRMWARE_UPDATE_PULL_SUPPORT if firmware pull is not required.

Fix this in Zephyr Scoped from the published advisory
  • Consultation3.0 h
  • Implementation2.0 h
  • Testing6.0 h
  • Review / QA3.0 h
14.0 hours of engineering $2,400
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-10672 in production — separate from our analysis above.

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