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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.

PUBLISHED Reserved 2026-04-17 | Published 2026-04-20 | Updated 2026-04-20 | Assigner AMZN




MEDIUM: 4.7CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N

MEDIUM: 5.7CVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

Problem types

CWE-757 Selection of Less-Secure algorithm during negotiation ('algorithm downgrade')

Product status

Default status
unaffected

2 (custom)
affected

3 (custom)
affected

4 (custom)
affected

Credits

1seal.org finder

References

aws.amazon.com/security/security-bulletins/2026-017-aws/ vendor-advisory

github.com/aws/aws-encryption-sdk-python/releases/tag/v4.0.5 patch

github.com/aws/aws-encryption-sdk-python/releases/tag/v3.3.1 patch

github.com/...python/security/advisories/GHSA-v638-38fc-rhfv third-party-advisory

cve.org (CVE-2026-6550)

nvd.nist.gov (CVE-2026-6550)

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