CVE-2026-11835

Caliptra Update-Reset Secure-Boot Bypass via Attacker-Chosen AXI Staging Address (TOCTOU)

MEDIUM
5.6
CVSS Score
Published: August 4, 2026 at 12:03 AM UTC
Updated: October 23, 2026 at 11:10 PM UTC
1 product affected across 1 vendorCore ROM

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Severity
MEDIUM5.6
Exploit prediction
EPSS 0.1%
SSVC
No known exploit

Description

Time-of-check time-of-use (TOCTOU) vulnerability combined with missing input validation in Caliptra Core ROM (UpdateResetFlow::run()) in subsystem mode allows a compromised local attacker to silently bypass secure boot by supplying an AXI staging address that is not validated against the strap-configured SS_EXTERNAL_STAGING_AREA_BASE_ADDR, enabling firmware to be modified between verification and loading into ICCM. Attestation continues to report the originally verified image digest, masking the compromise. Exploitation requires a compromised MCU firmware with AXI manager access to unprotected SRAM reachable by Caliptra. This issue affects Core ROM: 2.1.0 through 2.1.1.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

2.1.0 ≤ v ≤ 2.1.12.1.0
Vendor states this is fixed in 2.1.2 (unaffected)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.6MEDIUMCaliptra
Vector?

Quick Info

StatusAWAITING ANALYSIS
CWE
CWE-367CWE-20

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