# CVE-2026-6550

## Summary

- **CVE ID:** CVE-2026-6550
- **Severity:** MEDIUM
- **CVSS Score:** 5.7 (CVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N)
- **CWE:** CWE-757
- **Published:** Apr 20, 2026
- **Last Modified:** Apr 20, 2026

## Description

Cryptographic algorithm downgrade in the caching layer of Amazon AWS Encryption SDK for Python before version 3.3.1 and before version  4.0.5 might allow an authenticated local threat actor to bypass key commitment policy enforcement via a shared key cache, resulting in ciphertext that can be decrypted to multiple different plaintexts.

To remediate this issue, users should upgrade to version 3.3.1, 4.0.5 or above.

## Affected Products

- AWS — AWS Encryption SDK for Python (2)
- AWS — AWS Encryption SDK for Python (3)
- AWS — AWS Encryption SDK for Python (4)

## References

- [CNA](https://aws.amazon.com/security/security-bulletins/2026-017-aws/)
- [CNA](https://github.com/aws/aws-encryption-sdk-python/releases/tag/v4.0.5)
- [CNA](https://github.com/aws/aws-encryption-sdk-python/releases/tag/v3.3.1)
- [CNA](https://github.com/aws/aws-encryption-sdk-python/security/advisories/GHSA-v638-38fc-rhfv)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.10%
- **EPSS Percentile:** 0.8

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._