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VulnerabilityPublished

CVE-2026-6550: AWS Encryption SDK for Python · Algorithm Downgrade

Affects AWS Encryption SDK for PythonSource CVE Database V5

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Not known to be exploited · CVSS 4.7 Medium · patch available : update AWS Encryption SDK for Python when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
4.7Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.09% chance of exploitation in 30 days – higher than 0% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 20 Apr 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
AWSAWS Encryption SDK for PythonAffected
  • >=2 <=2.5.1
  • >=3 <=3.3.0
  • >=4 <=4.0.4
Fixed in–
PyPIaws-encryption-sdkpkg:pypi/aws-encryption-sdkOther threatsAffected
  • =2
  • =3
  • =4
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Users should upgrade the AWS Encryption SDK for Python to version 3.3.1, 4.0.5, or later to remediate this vulnerability. AWS manages remediation for their cloud services, but for local SDK usage, applying these updates is necessary. No other mitigation steps are indicated by the vendor advisory.

Description

CVE-2026-6550 is a cryptographic algorithm downgrade vulnerability in the caching layer of the AWS Encryption SDK for Python. It affects versions before 3.3.1 and before 4.0.5. An authenticated local attacker could exploit this to bypass key commitment policy enforcement via a shared key cache, causing ciphertext to decrypt to multiple different plaintexts. AWS has released fixed versions 3.3.1 and 4.0.5 to address this issue.

References

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