CVE-2026-6550 json
Key commitment policy bypass via shared key cache in AWS Encryption SDK for Python
published 2026-04-20 6 mo ago modified 2026-10-26 13 d ago also GHSA-v638-38fc-rhfv , PYSEC-2026-2387 , EUVD-2026-23943
- cvss
- 4.7
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.1%
- EPSS 0.1% chance of exploitation in 30 days, percentile 0%
- public exploits
- 0
- none known
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.
Patch / fix
- pypi aws-encryption-sdk 3.3.1, 4.0.5
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 6 mo ago
Exploit prediction
0.10% chance of exploitation in the next 30 days, higher than 0% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 4.7 | CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N |
| CNA | 4.0 | 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 |
| CNA | 4.0 | 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
| OSV | 3.1 | 4.7 | CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N |
| GitHub | 3.1 | 4.7 | CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| pypi | aws-encryption-sdk | >=2.0.0, <3.3.1 >=4.0.0, <4.0.5 |
3.3.1 4.0.5 |
Affected products
- AWS AWS Encryption SDK for Python
Classification
- Weakness
-
- CWE-757 Selection of Less-Secure Algorithm During Negotiation
References
-
github.com
/aws/aws-encryption-sdk-python/releases/tag/v4.0.5
patch, web
-
github.com
/aws/aws-encryption-sdk-python/releases/tag/v3.3.1
patch, web
-
aws.amazon.com
/security/security-bulletins/2026-017-aws/
vendor-advisory
-
github.com
/aws/aws-encryption-sdk-python/security/advisories/GHSA-v638-38fc-rhfv
third-party-advisory, web
-
github.com
/google/security-research/security/advisories/GHSA-wqgp-vphw-hphf
web
-
nvd.nist.gov
/vuln/detail/CVE-2026-6550
advisory
-
aws.amazon.com
/security/security-bulletins/2026-017-aws
web
-
github.com
/aws/aws-encryption-sdk-python
package
-
pypi.org
/project/aws-encryption-sdk
package
-
github.com
/advisories/GHSA-v638-38fc-rhfv
advisory
Sources
- CVE List CVE-2026-6550
- GitHub Advisory GHSA-v638-38fc-rhfv
- NVD CVE-2026-6550
- OSV PYSEC-2026-2387
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.