EchelonGraph verdictPlan mitigationRemediate within your standard update timelines (the SSVC decision on this page).
- •High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 8.1Exploit: None knownExposed services: Not assessed
A fix is referenced (a reference tagged "Patch", often a source commit), but no release containing it is confirmed — find the release that contains it; until it is applied, mitigate (WAF / firewall / segmentation).
The 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.
SSVC (CISA's decision table, applied by EchelonGraph)Track at every mission impact level.
A fix is referenced, but no release containing it is confirmed. Check the referenced fix and the vendor's advisory for a release that contains it and apply that within your standard update timelines; until then, restrict network exposure of the affected system or apply the vendor's mitigation.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it