NULL-pointer / out-of-bounds write in Zephyr MCTP I2C+GPIO target binding driven by an unauthenticated I2C controller

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-10678
StatePUBLISHED
Assignerzephyr
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-21 22:17:00 UTC
Updated2026-07-22 20:16:42 UTC
DescriptionThe MCTP-over-I2C+GPIO target binding in Zephyr (subsys/pmci/mctp/mctp_i2c_gpio_target.c) processes pseudo-register writes from an I2C bus master byte-by-byte in mctp_i2c_gpio_target_write_received() without validating the order or the receive buffer. In the affected versions the MCTP_I2C_GPIO_RX_MSG_ADDR (data) handler dereferences and writes through b->rx_pkt without checking that the receive buffer was allocated: a controller that selects the data register and writes a byte without first sending the length register (which is what allocates the buffer) causes a write of an attacker-chosen byte through a NULL/unallocated mctp_pktbuf pointer (i.e. into a small attacker-advanceable offset above address 0), producing memory corruption or a hard fault. The same handler also performs a write-then-check bounds test, allowing a one-byte heap overflow at data[255] when more than 255 data bytes are sent. Because the I2C target callback is invoked with raw bytes supplied by whatever device is the bus master and the binding performs no authentication, a malicious or malfunctioning controller on the bus can trigger these without any prior protocol state, leading to memory corruption and/or denial of service on the target device. The vulnerable code was introduced when the I2C+GPIO target binding was added and shipped in Zephyr v4.3.0 and v4.4.0. The fix defers allocation to the first data byte with a NULL check, treats a missing length as a zero-sized packet rejected by libmctp, and moves the bounds check before the store.

Risk And Classification

Primary CVSS: v3.1 8.1 HIGH from [email protected]

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

EPSS: 0.003300000 probability, percentile 0.253900000 (date 2026-07-22)

Problem Types: CWE-476 | CWE-787 | CWE-476 memory-safety | CWE-787 memory-safety

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary8.1HIGHCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
3.1CNACVSS8.1HIGHCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Adjacent
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Zephyrproject Zephyr affected 4.3.0 4.5.0 semver Not specified

References

ReferenceSourceLinkTags
github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-pmwm-5rcm-... [email protected] github.com
github.com/zephyrproject-rtos/zephyr/commit/9e23364261a2188c171d734d6947... [email protected] github.com
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