CVE-2026-6550: CWE-757 Selection of Less-Secure algorithm during negotiation ('algorithm downgrade') in AWS AWS Encryption SDK for Python
CVE-2026-6550 is a medium-severity vulnerability in the AWS Encryption SDK for Python that allows an authenticated local attacker to perform a cryptographic algorithm downgrade in the caching layer. This flaw affects versions before 3. 3. 1 and 4. 0. 5 and can lead to bypassing key commitment policy enforcement via a shared key cache, resulting in ciphertext that may decrypt to multiple different plaintexts. AWS has released fixed versions 3. 3. 1 and 4. 0.
AI Analysis
Technical Summary
This vulnerability involves a cryptographic algorithm downgrade in the caching layer of the AWS Encryption SDK for Python prior to versions 3.3.1 and 4.0.5. An authenticated local threat actor can exploit this by leveraging a shared key cache to bypass key commitment policy enforcement. This results in ciphertext that can be decrypted into multiple different plaintexts, undermining the integrity of encrypted data. The issue is tracked as CWE-757 (Selection of Less-Secure Algorithm during Negotiation). AWS manages remediation for this cloud-hosted service and has published an advisory recommending upgrading to fixed versions.
Potential Impact
The vulnerability allows an authenticated local attacker to bypass key commitment policy enforcement, potentially causing ciphertext to decrypt into multiple different plaintexts. This compromises the integrity of encrypted data but does not impact confidentiality or availability. The CVSS score is 4.7 (medium severity), reflecting the requirement for local authentication and high attack complexity.
Mitigation Recommendations
A fix is available. Users should upgrade the AWS Encryption SDK for Python to version 3.3.1, 4.0.5, or later as recommended by AWS in their security advisory (https://aws.amazon.com/security/security-bulletins/2026-017-aws/). Since this is a cloud-hosted service, AWS manages remediation for the service itself, but users must update their SDK versions to ensure protection.
CVE-2026-6550: CWE-757 Selection of Less-Secure algorithm during negotiation ('algorithm downgrade') in AWS AWS Encryption SDK for Python
Description
CVE-2026-6550 is a medium-severity vulnerability in the AWS Encryption SDK for Python that allows an authenticated local attacker to perform a cryptographic algorithm downgrade in the caching layer. This flaw affects versions before 3. 3. 1 and 4. 0. 5 and can lead to bypassing key commitment policy enforcement via a shared key cache, resulting in ciphertext that may decrypt to multiple different plaintexts. AWS has released fixed versions 3. 3. 1 and 4. 0.
CVSS v3.1
Score 4.7medium
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability involves a cryptographic algorithm downgrade in the caching layer of the AWS Encryption SDK for Python prior to versions 3.3.1 and 4.0.5. An authenticated local threat actor can exploit this by leveraging a shared key cache to bypass key commitment policy enforcement. This results in ciphertext that can be decrypted into multiple different plaintexts, undermining the integrity of encrypted data. The issue is tracked as CWE-757 (Selection of Less-Secure Algorithm during Negotiation). AWS manages remediation for this cloud-hosted service and has published an advisory recommending upgrading to fixed versions.
Potential Impact
The vulnerability allows an authenticated local attacker to bypass key commitment policy enforcement, potentially causing ciphertext to decrypt into multiple different plaintexts. This compromises the integrity of encrypted data but does not impact confidentiality or availability. The CVSS score is 4.7 (medium severity), reflecting the requirement for local authentication and high attack complexity.
Mitigation Recommendations
A fix is available. Users should upgrade the AWS Encryption SDK for Python to version 3.3.1, 4.0.5, or later as recommended by AWS in their security advisory (https://aws.amazon.com/security/security-bulletins/2026-017-aws/). Since this is a cloud-hosted service, AWS manages remediation for the service itself, but users must update their SDK versions to ensure protection.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- AMZN
- Date Reserved
- 2026-04-17T20:06:20.299Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
- Is Cloud Service
- true
- Vendor Advisory Urls
- [{"url":"https://aws.amazon.com/security/security-bulletins/2026-017-aws/","vendor":"AWS"}]
Threat ID: 69e6827f19fe3cd2cd2c9b8d
Added to database: 4/20/2026, 7:46:07 PM
Last enriched: 5/26/2026, 8:34:37 PM
Last updated: 6/4/2026, 8:08:57 AM
Views: 103
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