Security issues in AWS KMS and AWS Encryption SDKs: in-band protocol negotiation and robustness

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.6 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2020-8897: 0.40% estimated exploitation activity in the next 30 days; percentile 34.20 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Authors: Thai "thaidn" Duong Summary The following security vulnerabilities was discovered and reported to Amazon, affecting AWS KMS and all versions of AWS Encryption SDKs prior to version 2.0.0: Information leakage: an attacker can create ciphertexts that would leak the user’s AWS account ID, encryption context, user agent, and IP address upon decryption Ciphertext forgery: an attacker can create ciphertexts that are accepted by other users Robustness: an attacker can create ciphertexts that decrypt to different plaintexts for different users The first two bugs are somewhat surprising because they show that the ciphertext format can lead to vulnerabilities. These bugs (and the infamous alg: "None" bugs in JWT) belong to a class of vulnerabilities called in-band protocol negotiation. This is the second time we’ve found in-band protocol negotiation vulnerabilities in AWS cryptography libraries; see this bug in S3 Crypto SDK discovered by my colleague Sophie Schmieg. In JWT and S3 SDK…

Published by the source

12 Oct 2021, 16:01 UTC

Last modified by the source

10 Sep 2026, 03:49 UTC

Source last checked

26 Oct 2026, 13:16 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-wqgp-vphw-hphf

2. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-wqgp-vphw-hphf

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# Patch Next advisory brief: CVE-2020-8897

Advisory: Security issues in AWS KMS and AWS Encryption SDKs: in-band protocol negotiation and robustness
IDs: CVE-2020-8897, GHSA-wqgp-vphw-hphf
Record: https://patchnext.com/advisories/cve-2020-8897 (revision 3, source checked 26 Oct 2026, 13:16 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: com.amazonaws:aws-encryption-sdk-java 2.0.0; aws-encryption-sdk 2.0.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven com.amazonaws:aws-encryption-sdk-java: affected < 2.0.0; fixed in 2.0.0
- PyPI aws-encryption-sdk: affected < 2.0.0; fixed in 2.0.0

## Suggested inspection (read-only)
- Maven com.amazonaws:aws-encryption-sdk-java: check the installed version with your package manager.
- `python -m pip show aws-encryption-sdk`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on com.amazonaws:aws-encryption-sdk-java, aws-encryption-sdk.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-wqgp-vphw-hphf (OSV record GHSA-wqgp-vphw-hphf lists affected ranges: Maven com.amazonaws:aws-encryption-sdk-java >=0 =0 <2.0.0 (fixed))
- Verified: https://github.com/advisories/GHSA-wqgp-vphw-hphf (GitHub-reviewed advisory GHSA-wqgp-vphw-hphf lists affected ranges: Maven com.amazonaws:aws-encryption-sdk-java >=0 =0 <2.0.0)

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