CVE-2026-6458 — AES-256-GCM Authentication Tag Does Not Cover First Ciphertext Blocks When AAD Is Empty

Description (CNA)

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.

Affected (CNA)

Vendor / product	Versions
Caliptra / Core Runtime Firmware	affected 2.0.0 through 2.0.1; affected 2.1.0; unaffected 2.0.2; unaffected 2.1.1

CWE

CWE-325

References

https://github.com/chipsalliance/caliptra-sw/security/advisories/GHSA-834g-h5x6-2hqr

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.