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CVE.org (no NVD analysis yet)· CNA zephyr

CVE-2026-17053: SMBus callback-removal syscalls accept an unvalidated user pointer, letting user threads manipulate kernel callback state

MediumCVSS 4.4 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 17/100)

  • 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: 0.09% (FIRST EPSS).
  • Someone with local access to the system 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 zephyr 4.3.2, 4.4.2.

Low priority for now. Upgrade to zephyrproject zephyr 4.3.2, 4.4.2 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

The SMBus driver API exposed smbus_smbalert_remove_cb() and smbus_host_notify_remove_cb() as Zephyr syscalls. Their verifiers in drivers/smbus/smbus_handlers.c validated only the dev argument with K_SYSCALL_OBJ(dev, K_OBJ_DRIVER_SMBUS) and forwarded the caller-supplied struct smbus_callback *cb pointer into kernel-mode driver code without any K_SYSCALL_MEMORY_READ/K_SYSCALL_MEMORY_WRITE validation. A companion change in 2023 had already removed the matching smbus_smbalert_set_cb() / smbus_host_notify_set_cb() syscalls for this reason, but the two removal syscalls were left exposed. On a build with CONFIG_USERSPACE=y, CONFIG_SMBUS=y and a driver implementing the callback operations (drivers/smbus/intel_pch_smbus.c with CONFIG_SMBUS_INTEL_PCH_SMBALERT/CONFIG_SMBUS_INTEL_PCH_HOST_NOTIFY, or drivers/smbus/smbus_stm32.c with CONFIG_SMBUS_STM32_SMBALERT), any user-mode thread that has been granted the SMBus device object can invoke these syscalls with an arbitrary pointer. The value reaches smbus_callback_remove() in drivers/smbus/smbus_utils.h, which uses it as a node identity against the kernel's sys_slist_t of registered callbacks. The consequence is that an unprivileged thread can unregister an SMBALERT or Host Notify callback that a supervisor-mode component registered, silently disabling alert handling for the rest of the system; because Zephyr images have fixed symbol addresses and the syscall returns 0 on a hit versus -ENOENT on a miss, the target address is both derivable and searchable. In builds with CONFIG_ASSERT=y the __ASSERT(callback->handler, ...) check additionally dereferences the caller-supplied address in supervisor mode, so a bogus pointer raises a kernel-mode fault and a fatal system error, and the fault/no-fault outcome discloses which addresses are mapped. The fix removes both syscall entry points, demoting the two functions to ordinary static inline calls so that callback list manipulation is available only to supervisor-mode code. There is no impact on builds without CONFIG_USERSPACE, and no impact on configurations that do not enable an SMBus driver with SMBALERT or Host Notify support.

Published
Oct 1, 2026
Updated
Nov 4, 2026
EPSS
0.0% · 0th percentile

Report tools

JSON

Action score

17

Monitor

Low priority for now.

CVSS
17 / 40 · 4.4 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.0%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · zephyr
4.4
NVD has not scored this yet; the score shown is the CNA’s.

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 exploit code appears or is weaponized
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  • 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.

—

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 zephyr

    • 3.4.0 and later · before 4.3.2affected · semver
    • 4.4.0 and later · before 4.4.2affected · semver

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-2026-18746Sep 29, 2026 · NULL pointer dereference in Zephyr LwM2M client when the CoAP Block1 context pool is exhausted
    23Monitor
  • ← EarlierCVE-2026-18747Sep 29, 2026 · Integer underflow of net_buf length in the MCUmgr serial (SMP over console) transport leads to out-of-bounds read
    24Monitor
  • Later →CVE-2026-19184Oct 5, 2026 · Out-of-bounds write in the NXP GAU ADC driver due to byte-versus-sample buffer size validation mismatch
    33Monitor

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 zephyr4.3.2Vendor (CNA)
zephyrproject zephyr4.4.2Vendor (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.

  1. Published
  2. Fix recordedsame day
  3. TodayNov 13, 2026+43 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

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

Variant candidates

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

  • CVE-2026-1263144 days apartBroken access-control denial in k_thread_join/k_thread_abort syscall validation in Zephyr kernel
    26Monitor
  • CVE-2026-1994720 days apartMissing kernel object permission check in devmux syscalls allows unprivileged user threads to retarget a device multiplexer
    21Monitor

Not on record for this CVE: researcher credit · public bounty program.

Technical details

Attack conditions

  • Someone with local access to the system 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
none
Integrity
low · data or configuration can be modified
Availability
low · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
Low
Availability impact
Low

Weakness class (CWE)

CWE-862 · Missing Authorization

CVSS vector

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

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Change log

  1. SSVC exploitation— → none
  2. Exploit maturity— → none
  3. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (1 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

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