CVE-2026-4270
Description
Improper Protection of Alternate Path exists in the no-access and workdir feature of the AWS API MCP Server versions >= 0.2.14 and < 1.3.9 on all platforms may allow the bypass of intended file access restriction and expose arbitrary local file contents in the MCP client application context. To remediate this issue, users should upgrade to version 1.3.9.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
No mitigations published for this CVE yet.
The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.
✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here withsource_tier=community-verified.
Package impact
| Ecosystem | Package | Vulnerable | Fixed |
|---|---|---|---|
| PyPI | awslabs-aws-api-mcp-server | >=0.2.14,<1.3.9 | 1.3.9 |
Application impact
| Vendor | Product | Versions | Fixed |
|---|---|---|---|
| amazon | aws_api_mcp_server | {"startIncluding":"0.2.14","endExcluding":"1.3.9"} | 1.3.9 |
| aws | api-mcp-file-access-restriction-bypass | | |
References
- https://github.com/awslabs/mcp/security/advisories/GHSA-2cpp-j2fc-qhp7
- https://nvd.nist.gov/vuln/detail/CVE-2026-4270
- https://aws.amazon.com/security/security-bulletins/2026-007-AWS
- https://github.com/awslabs/mcp
- https://pypi.org/project/awslabs.aws-api-mcp-server/1.3.9
- https://aws.amazon.com/security/security-bulletins/2026-007-AWS/
- https://pypi.org/project/awslabs.aws-api-mcp-server/1.3.9/
CWEs
CWE-424
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.