Minimal basti IAM Policy Allows Shell Access

Exploitation

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

CVSS

not scored

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Summary The provided Minimal IAM Policy for bastic connect does not include ssm:SessionDocumentAccessCheck. This results in the ability to get a shell session on the bastion, not just the intended access for Port Forwarding. Details basti connect is designed to "securely connect to your RDS/Aurora/Elasticache/EC2 instances", using a bastion instance "with AWS Session Manager port forwarding capability to make the target available on your localhost." The Minimal IAM Policy allows port forwarding via the following statement: This statement does not include the following condition: As a result, the basti connect minimal policy is logically identical to: A basti admin would expect users under the minimal policy to be able to port forward. However, they could also get a shell on the bastion. For more details on this footgun, see: https://ramimac.me/ssm-iam PoC Complete instructions, including specific configuration details, to reproduce the vulnerability. Impact Impact would depend on…

Published by the source

24 Aug 2023, 12:53 UTC

Last modified by the source

24 Aug 2023, 12:53 UTC

Source last checked

26 Oct 2026, 12:24 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-q4pp-j36h-3gqg

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-q4pp-j36h-3gqg

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# Patch Next advisory brief: GHSA-q4pp-j36h-3gqg

Advisory: Minimal `basti` IAM Policy Allows Shell Access
IDs: GHSA-q4pp-j36h-3gqg
Record: https://patchnext.com/advisories/ghsa-q4pp-j36h-3gqg (revision 2, source checked 26 Oct 2026, 12:24 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Unrated
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: basti-cdk 1.0.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm basti-cdk: affected < 1.0.1; fixed in 1.0.1

## Suggested inspection (read-only)
- `npm ls basti-cdk --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## 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 basti-cdk.
- 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-q4pp-j36h-3gqg (OSV record GHSA-q4pp-j36h-3gqg lists affected ranges: npm basti-cdk >=0 <1.0.1 (fixed))
- Verified: https://github.com/advisories/GHSA-q4pp-j36h-3gqg (GitHub-reviewed advisory GHSA-q4pp-j36h-3gqg lists affected ranges: npm basti-cdk >=0 <1.0.1)

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