CVE-2026-6458 json
AES-256-GCM Authentication Tag Does Not Cover First Ciphertext Blocks When AAD Is Empty
published 2026-06-23 4 mo ago modified 2026-10-25 14 d ago also EUVD-2026-38637
- cvss
- 5.1
- version 4.0, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 9%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- Caliptra Core Runtime Firmware 2.0.2, 2.1.1
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 4 mo ago
Exploit prediction
0.20% chance of exploitation in the next 30 days, higher than 9% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 5.1 | 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 |
| CNA | 4.0 | 5.1 | 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
Affected products
- Caliptra Core Runtime Firmware
Classification
- Weakness
-
- CWE-325 Missing Cryptographic Step
References
Sources
- CVE List CVE-2026-6458
- NVD CVE-2026-6458
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