CVE-2026-6458
AES-256-GCM Authentication Tag Does Not Cover First Ciphertext Blocks When AAD Is Empty
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.
Attack profile
How easy it is to exploit
- Attack vector
- Adjacent network
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- Low
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
AES-256-GCM Authentication Tag Does Not Cover First Ciphertext Blocks When AAD Is Empty
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.
- Record
CVE-2026-6458- CVSS 4.0
- 5.1 Medium
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 - Weakness
- CWE-325
- Updated
- 2026-11-02
EUVDEUVD-2026-38637
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.
- Record
EUVD-2026-38637- CVSS 4.0
- 5.1 Medium
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 - Updated
- 2026-11-02
NVD
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.
- Record
CVE-2026-6458- CVSS 4.0
- 5.1 Medium
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 - Weakness
- CWE-325
- Updated
- 2026-11-02
OSV
AES-256-GCM Authentication Tag Does Not Cover First Ciphertext Blocks When AAD Is Empty
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.
- Record
CVE-2026-6458- CVSS 4.0
- 5.1 Medium
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 - Weakness
- CWE-325
- Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-6458 is a medium vulnerability (CVSS 5.1) in Caliptra Core Runtime Firmware, published June 23, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.20%, the 9th percentile. No source names a fixed version.