CVE-2026-6458 AES-256-GCM Authentication Tag Does Not Cover First Ciphertext Blocks When AAD Is Empty
Attackers can modify initial ciphertext blocks without detection due to incorrect GCM tag calculation when AAD is empty in Caliptra firmware.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-6458?
CVE-2026-6458 is a medium-severity vulnerability in Caliptra Core Runtime Firmware, published on 23 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
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.
Weakness: CWE-325
Which versions are affected by CVE-2026-6458?
How do I fix CVE-2026-6458?
No fix has been published for CVE-2026-6458 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-6458 being exploited?
There is no known exploitation of CVE-2026-6458 in the wild and no public exploit code.
Sources
Also known as GHSA-834g-h5x6-2hqr.