Caliptra Core Firmware EUVD-2026-47746

Exploitation requires: (1) the target device must be running Caliptra Core Runtime Firmware in subsystem mode - this is a specific operational deployment mode, not the default standalone configuration; (2) the attacker must have privileged local access sufficient to issue commands via the Caliptra mailbox interface, which in practice means control over firmware running on the SoC or direct physical access to the mailbox mechanism; (3) the attack targets one of three specific command handlers: INVOKE_DPE_MLDSA87, CM_AES_GCM_DECRYPT_DMA, or EXTERNAL_MAILBOX_CMD. What limits exploitation: remote network access cannot directly reach the Caliptra mailbox; unprivileged local access is insufficient (PR:L per CVSS 4.0 confirms low privileges, meaning some authenticated foothold is required but not full root/admin); and impact beyond DoS is integration-specific - not all deployments will experience the SI:L subsequent-system integrity effect.

The CVSS 4.0 score of 6.8 with vector AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:L/SA:N is internally consistent with the description: local access is required, low complexity once inside, and the primary confirmed impact is high availability loss against the vulnerable Caliptra component. The SI:L (subsequent-system integrity: low) metric acknowledges that integration-specific downstream effects are possible but not universally guaranteed - the vendor explicitly qualifies this. EPSS data is absent; given the niche deployment footprint and the need for local privileged access to the SoC's firmware environment, opportunistic mass exploitation is highly unlikely. There is no CISA KEV listing and no public proof-of-concept identified at time of analysis. Real-world risk is highest in hyperscaler or cloud-hardware supply-chain scenarios where an insider or compromised firmware build process could leverage this to disable attestation for a server node. For typical enterprise environments this is currently a low-priority finding due to access prerequisites; for silicon vendors shipping Caliptra-integrated chips it is a medium-priority firmware correctness issue requiring a patch cycle.

An attacker who has gained privileged local execution on a SoC running Caliptra in subsystem mode - such as through a compromised higher-level firmware component or an insider with firmware flash access - crafts a mailbox command targeting one of the three vulnerable handlers with an AXI address pointing outside the expected memory region. The Caliptra firmware processes the unverified address, triggering a fault or memory access violation that crashes the Root of Trust runtime, disabling hardware attestation and key management services for the duration of the outage. No public proof-of-concept is available at time of analysis.