# AWS Encryption SDK for Python: Key commitment policy bypass via shared key cache

Advisory record · `GHSA-v638-38fc-rhfv`

- **Identifiers:** `GHSA-v638-38fc-rhfv` · `CVE-2026-6550` · `PYSEC-2026-2387`
- **State:** Confirmed
- **Severity:** CVSS 5.7 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-757](https://cwe.mitre.org/data/definitions/757.html)
- **Tags:** [CWE-757](https://agentprime.io/advisories/tag/cwe-757.md)
- **Published:** 24 Apr 2026
- **Updated:** 13 Jul 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 24 Apr 2026, 15:59 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `aws-encryption-sdk` (PyPI): affected `>=2.0.0, <3.3.1 || >=4.0.0, <4.0.5`; fixed in `3.3.1`, `4.0.5`

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 5.7 Medium, CVSS 4.0: `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`, from CNA (AMZN)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0010, the 1st percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 15:02 UTC: First seen by agentprime
- 31 Oct 2026, 15:02 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-v638-38fc-rhfv)

## Sources

- [GitHub Advisory Database: GHSA-v638-38fc-rhfv](https://github.com/advisories/GHSA-v638-38fc-rhfv)
- [OSV: GHSA-v638-38fc-rhfv](https://osv.dev/vulnerability/GHSA-v638-38fc-rhfv)
- <https://github.com/aws/aws-encryption-sdk-python/security/advisories/GHSA-v638-38fc-rhfv>
- <https://github.com/google/security-research/security/advisories/GHSA-wqgp-vphw-hphf>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-6550>
- <https://aws.amazon.com/security/security-bulletins/2026-017-aws>
- <https://github.com/aws/aws-encryption-sdk-python>
- <https://github.com/aws/aws-encryption-sdk-python/releases/tag/v3.3.1>
- <https://github.com/aws/aws-encryption-sdk-python/releases/tag/v4.0.5>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-v638-38fc-rhfv>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-v638-38fc-rhfv/>. Everything for agents: <https://agentprime.io/llms.txt>.