CVE-2026-6458

AES-256-GCM Authentication Tag Does Not Cover First Ciphertext Blocks When AAD Is Empty

Published Jun 23, 2026 CVSS 4.0 · 5.1 Medium EPSS < 1% KEV · Not listed
Description
Missing cryptographic step in Caliptra Core Firmware (aes_256_gcm_update module) results in an incorrect GCM authentication tag. When the streaming AES-256-GCM API is used with empty AAD, the hardware GHASH accumulator state is not saved after the first update call, causing the final tag to exclude the first batch of processed ciphertext. Ciphertext produced by that call may be modified without the tag reflecting the change.

This issue affects Core Runtime Firmware: from 2.0.0 through 2.0.1, 2.1.0.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
First Time appeared Caliptra
Caliptra core Runtime Firmware
Vendors & Products Caliptra
Caliptra core Runtime Firmware
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description Missing cryptographic step in Caliptra Core Firmware (aes_256_gcm_update module) results in an incorrect GCM authentication tag. When the streaming AES-256-GCM API is used with empty AAD, the hardware GHASH accumulator state is not saved after the first update call, causing the final tag to exclude the first batch of processed ciphertext. Ciphertext produced by that call may be modified without the tag reflecting the change. This issue affects Core Runtime Firmware: from 2.0.0 through 2.0.1, 2.1.0.
Title AES-256-GCM Authentication Tag Does Not Cover First Ciphertext Blocks When AAD Is Empty
Weaknesses CWE-325
References
Metrics cvssV4_0

{'score': 5.1, 'vector': 'CVSS:4.0/AV:A/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
Caliptra
Published
Updated
Jun 24, 2026, 1:15 PM
Reserved
Apr 16, 2026, 9:11 PM
Status
Awaiting Analysis
Published
Jun 24, 2026, 12:16 AM
Modified
Oct 25, 2026, 11:10 PM