Key commitment policy bypass via shared key cache in AWS Encryption SDK for Python
Priority LOW 24CWE-757Published · Updated
Key facts
- Attack vector
- Local
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- High
- Attack requirements
- Present
- Impact type
- —
- Confidentiality · integrity · availability
- None · High · None
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub.
Summary
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.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00096 0th percentileScored 2026-11-07
Fix Fixed aws-encryption-sdk (PyPI): 3.3.1, 4.0.5
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| AWS | AWS Encryption SDK for Python | 2 – 2.5.1; 3 – 3.3.0; 4 – 4.0.4 | — | No fix listed | CNA |
| — | aws-encryption-sdk (PyPI) | 2.0.0 to before 3.3.1 | 3.3.1 | Patch available | GHSA-v638-38fc-rhfv |
| — | aws-encryption-sdk (PyPI) | 4.0.0 to before 4.0.5 | 4.0.5 | Patch available | GHSA-v638-38fc-rhfv |
- AWS Encryption SDK for Python VendorAWS Affected 2 – 2.5.1; 3 – 3.3.0; 4 – 4.0.4 Fixed in — No fix listed CNA
- aws-encryption-sdk (PyPI) Vendor— Affected 2.0.0 to before 3.3.1 Fixed in 3.3.1 Patch available GHSA-v638-38fc-rhfv
- aws-encryption-sdk (PyPI) Vendor— Affected 4.0.0 to before 4.0.5 Fixed in 4.0.5 Patch available GHSA-v638-38fc-rhfv
Remediation
- Fix · GHSA-v638-38fc-rhfv aws-encryption-sdk (PyPI) Fixed in 3.3.1 Advisory →
- Fix · GHSA-v638-38fc-rhfv aws-encryption-sdk (PyPI) Fixed in 4.0.5 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-6550
- 2026-10-03 Alias added: GHSA-v638-38fc-rhfv
References
Patch 2
Advisory 3
More AWS vulnerabilities
- TI-2026-23989 crypto: algif_aead - Revert to operating out-of-place KEVCVSS 3.1HIGH 7.8
- TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
- TI-2024-18648 Amazon AWS Amplify CLI before 12.10.1 incorrectly configures the role trust policy of IAM… CVSS 3.1CRITICAL 9.8
- TI-2024-05929 Openssh: regresshion - race condition in ssh allows rce/dos CVSS 3.1HIGH 8.1
- TI-2025-03847 Input validation issue in AWS Amplify Studio UI component properties CVSS 4.0CRITICAL 9.0
- TI-2026-11603 HTTP/2 Stream Parser Confusion Body-Inspection Bypass in Amazon CloudFront with AWS WAF CVSS 4.0HIGH 7.9
Sources
- CVE-2026-6550 · CVE Program
- CVE-2026-6550 · NVD
- FIRST EPSS
- GHSA-v638-38fc-rhfv · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences