AES-256-GCM Authentication Tag Does Not Cover First Ciphertext Blocks When AAD Is Empty
Key facts
- Attack vector
- Adjacent network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- —
- Confidentiality · integrity · availability
- None · Low · None
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA.
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
Remediation
- Fix · CNA Core Runtime Firmware (Caliptra) Fixed in 2.0.2, 2.1.1
Timeline
- 2026-10-02 Threatist record created from CVE-2026-6458
References
More Caliptra vulnerabilities
- TI-2026-05099 MCU Firmware Update Authentication Bypass on Caliptra Core CVSS 4.0HIGH 7.2
- TI-2026-06435 Unverified AXI Address in Subsystem Mode Commands Enables Denial of Service CVSS 4.0MEDIUM 6.8
- TI-2026-10213 Caliptra Update-Reset Secure-Boot Bypass via Attacker-Chosen AXI Staging Address (TOCTOU) CVSS 4.0MEDIUM 5.6
- TI-2026-10214 Production Debug-Unlock Token Verification Missing Device Binding CVSS 4.0LOW 1.8
Sources
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences