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Vulnerability · Published Jun 23, 2026 · Assigned by Caliptra

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

Medium 5.1

In plain English

A medium-severity security flaw in Core Runtime Firmware from Caliptra. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 10% of all known vulnerabilities).

Severity (CVSS 4.0)5.1Medium
Exploit odds (30 days)0.2%top 90.5% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

VendorProductVersions
Caliptra Core Runtime Firmware 2.0.0 – through 2.0.12.1.0

Weakness: CWE-325 · 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

References