CVE-2026-16584 json
AWS API MCP Server Security Policy Bypass via Startup Failure
published 3mo ago modified 16d ago also GHSA-29w2-fq35-v728 , PYSEC-2026-3549 , EUVD-2026-48299
- cvss
- 7.0
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 13%
- public exploits
- 0
- none known
Summary
Improper handling of an initialization failure in AWS API MCP Server from 0.2.13 through 1.3.46 might allow an actor to bypass the user-configured security policy and execute AWS API operations that the policy was set to deny or gate. When initialization of the security policy enforcement data fails at server startup, the policy check is skipped for the lifetime of the process. IAM permissions on the configured credentials remain in effect and are unaffected.
To remediate this issue, users should upgrade to version 1.3.47.
Patch / fix
- pypi awslabs-aws-api-mcp-server 1.3.47
- AWS aws-api-mcp-server 1.3.47
- github.com/awslabs/mcp@ab1bbeb commit
- pypi.org/project/awslabs.aws-api-mcp-server/1.3.47/ patch
- github.com/awslabs/mcp#4315 pull request
Is CVE-2026-16584 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerCISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- total
- Assessed
- 3mo ago
Exploit prediction
0.23% chance of exploitation in the next 30 days, higher than 13% of all scored CVEs (FIRST EPSS, 2026-11-09).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 7.0 | CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H |
| CNA | 4.0 | 7.3 | CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N |
| CNA | 4.0 | 7.3 | CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
| GitHub | 3.1 | 7.0 | CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H |
| OSV | 3.1 | 7.0 | CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| pypi | awslabs-aws-api-mcp-server | >=0.2.13, <1.3.47 |
1.3.47 |
Affected products
- AWS aws-api-mcp-server
Classification
- Weakness
-
- CWE-455 Non-exit on Failed Initialization
References
-
pypi.org
/project/awslabs.aws-api-mcp-server/1.3.47/
release-notes, patch
-
github.com
/awslabs/mcp/pull/4315
web
-
github.com
/awslabs/mcp/commit/ab1bbebc097d674c1cdd4bd75a8f313be18473bf
web
-
aws.amazon.com
/security/security-bulletins/2026-063-aws/
vendor-advisory
-
github.com
/awslabs/mcp/security/advisories/GHSA-29w2-fq35-v728
release-notes, web
-
nvd.nist.gov
/vuln/detail/CVE-2026-16584
advisory
-
aws.amazon.com
/security/security-bulletins/2026-063-aws
web
-
github.com
/awslabs/mcp
package
-
pypi.org
/project/awslabs.aws-api-mcp-server/1.3.47
web
-
pypi.org
/project/awslabs-aws-api-mcp-server
package
-
github.com
/advisories/GHSA-29w2-fq35-v728
advisory
Sources
- CVE List CVE-2026-16584
- GitHub Advisory GHSA-29w2-fq35-v728
- NVD CVE-2026-16584
- OSV PYSEC-2026-3549
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