Timing Side-Channel in AES-CCM Tag Verification in AWS-LC

### Summary AWS-LC is an open-source, general-purpose cryptographic library. ### Impact Observable timing discrepancy in AES-CCM decryption in AWS-LC allows an unauthenticated user to potentially determine authentication tag validity via timing analysis. The impacted implementations are through the EVP CIPHER API: EVP_aes_128_ccm, EVP_aes_192_ccm, and EVP_aes_256_ccm. Customers of AWS services do not need to take action. Applications using AWS-LC should upgrade to the most recent release of AWS-LC. ### Impacted versions From v1.21.0 through v1.68.0. From AWS-LC-FIPS-3.0.0 through AWS-LC-FIPS-3.1.0. ### Patches The patch is included in v1.69.0 and AWS-LC-FIPS-3.2.0. ### Workarounds In the special cases of using AES-CCM with (M=4, L=2), (M=8, L=2), or (M=16, L=2), applications can workaround this issue by using AES-CCM through the EVP AEAD API using implementations EVP_aead_aes_128_ccm_bluetooth, EVP_aead_aes_128_ccm_bluetooth_8, and, EVP_aead_aes_128_ccm_matter respectively. Otherwise, there is no workaround and applications using AWS-LC should upgrade to the most recent releases of AWS-LC. ### References If you have any questions or comments about this advisory, we ask that you contact AWS Security via our [vulnerability reporting page](https://aws.amazon.com/security/vulnerability-reporting) or directly via email to [aws-security@amazon.com](mailto:aws-security@amazon.com). Please do not create a public GitHub issue. ### Acknowledgement We would like to thank Joshua Rogers (https://joshua.hu/) of AISLE Research Team (https://aisle.com) for collaborating on this issue through the coordinated vulnerability disclosure process.

CVSS 3.1

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

Severity from

GitHub (reviewed advisory)

• github.com/aws/aws-lc/security/advisories/GHSA-frmv-5gcm-jwxh
• github.com/aws/aws-lc