Caliptra Core ROM CVE-2026-11836

Q: What is the CVSS score of CVE-2026-11836?

CVE-2026-11836 has a CVSS 4.0 base score of 1.8 (Low). CVSS vector: CVSS:4.0/AV:L/AC:L/AT:P/PR:H/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X. EPSS exploitation probability: 0.1%.

EUVD-2026-52548 LOW

Insufficient Verification of Data Authenticity (CWE-345)

2026-08-04 Caliptra

Information Disclosure Core Firmware Core Rom Caliptra

1.8

CVSS 4.0 · Vendor: Caliptra

Severity by source

Vendor (Caliptra) PRIMARY

1.8 LOW

CVSS:4.0/AV:L/AC:L/AT:P/PR:H/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

vuln.today AI

3.0 LOW

Local vector with high complexity (shared key-hash and subsystem-mode preconditions) and high privileges (signing service access); limited confidentiality and integrity impact only, no availability impact.

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

4.0 AV:L/AC:L/AT:P/PR:H/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (Caliptra).

CVSS VectorVendor: Caliptra

Attack Vector

Local

Attack Complexity

Low

Privileges Required

High

User Interaction

None

Scope

Lifecycle Timeline

Analysis Generated

Aug 04, 2026 - 00:29 vuln.today

DescriptionCVE.org

Insufficient verification of data authenticity in Caliptra Core ROM and Core Firmware (validate_debug_unlock_token()) in subsystem mode allows an attacker with access to the integrator's debug unlock signing service to unlock production debug on an unintended device by presenting a valid token issued for a different device sharing the same debug unlock key hash. The 384-bit challenge nonce continues to prevent replay of previously issued tokens. Practical impact is limited to loss of per-device scope enforcement within a set of devices that share the same unlock authority by design; it does not enable debug unlock on devices outside that set.

This issue affects Core ROM: 2.0.0 through 2.0.2, 2.1.0 through 2.1.1; Core Firmware: 2.0.0 through 2.0.1, 2.1.0.

AnalysisAI

Debug unlock token cross-device reuse in Caliptra Core ROM and Core Firmware (subsystem mode) allows an attacker who already holds access to an integrator's debug unlock signing service to unlock production debug on an unintended device by presenting a token originally issued for a different device sharing the same debug unlock key hash. The 384-bit challenge nonce prevents replay of previously captured tokens but does not bind a token to a specific target device identity, enabling lateral debug access within a shared-key-hash trust group. No public exploit has been identified and the CVSS 4.0 score of 1.8 reflects the narrow real-world impact, which is bounded by the requirement for high-privilege signing-service access and the hard constraint that exploitation cannot cross key-hash group boundaries.

Technical ContextAI

Caliptra is an open-source silicon Root of Trust (RoT) specification and implementation maintained by the CHIPS Alliance, designed to provide hardware security primitives for data center silicon. In subsystem mode, the validate_debug_unlock_token() function in Core ROM and Core Firmware is responsible for authorizing production debug unlock requests. CWE-345 (Insufficient Verification of Data Authenticity) describes the root cause: the function verifies that the presented token is cryptographically valid under the device's debug unlock key hash but does not bind the token to the specific target device's identity. As a result, any device sharing the same debug unlock key hash is treated as an equally valid recipient. Affected products are enumerated in CPE strings cpe:2.3:a:caliptra:core_rom and cpe:2.3:a:caliptra:core_firmware, covering Core ROM 2.0.0-2.0.2 and 2.1.0-2.1.1, and Core Firmware 2.0.0-2.0.1 and 2.1.0.

RemediationAI

Consult the upstream Caliptra security advisory at https://github.com/chipsalliance/caliptra-sw/security/advisories/GHSA-hw68-jjx4-m376 for patched releases; a specific fixed version number was not confirmed from the provided data, so the advisory should be reviewed directly to obtain the exact patch target. As an immediate architectural compensating control, integrators operating in subsystem mode can eliminate cross-device token reuse by ensuring each production device is provisioned with a unique debug unlock key hash rather than a shared one - this removes the shared-authority relationship that is the necessary precondition for exploitation, though it may increase key management overhead. Additionally, access to the debug unlock signing service should be restricted to the minimum necessary personnel with comprehensive audit logging of all token issuances, reducing the attacker's opportunity to obtain a valid cross-device token.