CVE-2026-6550

Medium

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.

SeverityMedium

CVSS4.7

Exploit probability—

ProductAws-encryption-sdk

PublishedApr 20, 2026

First seenApr 20, 2026

Weakness typeCWE-757CWE-757

How to fix

Update

aws-encryption-sdk3.3.1, 4.0.5 or later

Patches

Vendor advisories

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

Affected products

Product	Affected versions	Fixed in
aws-encryption-sdkPyPI	2.0.0 ≤ v < 3.3.1, 4.0.0 ≤ v < 4.0.5	3.3.1, 4.0.5

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