EchelonGraph verdictMonitorNo release containing the referenced fix is confirmed: check the referenced fix and the vendor's advisory for a release that contains it; until one is applied, restrict network exposure of the affected system or apply the vendor's mitigation on your normal schedule (the SSVC decision on this page).
- •Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.1%CVSS: 5.3Exploit: 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 device multiplexer pseudo-driver in drivers/misc/devmux/devmux.c exposes two system calls, devmux_select_get() and devmux_select_set(). When CONFIG_USERSPACE is enabled, their user-mode verifiers z_vrfy_devmux_select_get() and z_vrfy_devmux_select_set() forwarded directly to the kernel implementations without performing any kernel-object validation — no k_object_access_check() and no driver object check. Compounding this, DEVICE_DT_INST_DEFINE() registered devmux instances with a NULL driver API pointer, which causes scripts/build/gen_kobject_list.py to skip them entirely, so a devmux device had no struct k_object and no permission on it could be granted or withheld in the first place.
Any thread running in user mode can reach the defect: device pointers such as DEVICE_DT_GET(DT_NODELABEL(devmux0)) are compile-time constants available to application code, and the syscall accepted them from a thread that had never been granted access to the device. The kernel implementations do validate the pointer against the static devmux instance table and bounds-check the selection index, so this is not a memory-safety issue; the failure is purely one of authorization. Exposure requires CONFIG_USERSPACE=y together with the experimental CONFIG_DEVMUX=y (which depends on CONFIG_DEVICE_MUTABLE) and a zephyr,devmux devicetree node.
An unprivileged user-mode thread can read and change which downstream device a multiplexer forwards to, bypassing the userspace object-permission model. Because a devmux forwards the data, configuration and API of the selected device — its documented use being zephyr,console and zephyr,shell-uart switching — an attacker can suppress console, log and shell output, redirect that output to a downstream device it is able to observe, or flip the selection underneath another thread that is legitimately using the multiplexer. The impact is bounded to the devicetree-fixed set of downstream devices; no out-of-bounds access or arbitrary pointer dereference is reachable.
The fix declares __subsystem struct devmux_driver_api and attaches a DEVICE_API(devmux, devmux_api) instance to each devmux device so that it becomes a tracked K_OBJ_DRIVER_DEVMUX kernel object, and adds K_OOPS(devmux_inst_get(dev) == SIZE_MAX) plus K_OOPS(k_object_access_check(dev) != 0) to both verifiers.
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (5.3): severity, escalated by confirmed exploitation. This CVE's 5.3 is its impact severity (EG Severity), not escalated.
- EG Severity
- 5.3 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.a secondary CVSS source · CVSS v3.0 or v3.1
- EG Likelihood
- 0.1% within 30 daysSource: FIRST EPSS. FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at every mission impact level.CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.No released fix is confirmed on this page, but CISA's timeline does not wait for a fix's release: it starts when an agency identifies the flaw on an asset and updates the CDM Agency and Federal Dashboard, and the directive counts patching, decommissioning the system or another action as remediation. Until a fixed release is applied, mitigate as this page's verdict says. In the directive's words, “Fix on system upgrade” means that, “unless conditions change”, the vulnerability “should be remediated the next time the vulnerable asset receives a scheduled major upgrade or rebuild”: its timelines are “dynamic as facts change”, and a KEV listing shortens them.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
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; until one is applied, restrict network exposure of the affected system or apply the vendor's mitigation on your normal schedule.
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.
No released fix is confirmed on this page, but CISA's timeline does not wait for a fix's release: it starts when an agency identifies the flaw on an asset and updates the CDM Agency and Federal Dashboard, and the directive counts patching, decommissioning the system or another action as remediation. Until a fixed release is applied, mitigate as this page's verdict says. In the directive's words, “Fix on system upgrade” means that, “unless conditions change”, the vulnerability “should be remediated the next time the vulnerable asset receives a scheduled major upgrade or rebuild”: its timelines are “dynamic as facts change”, and a KEV listing shortens them.
The score's inputs: 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