CVE-2026-4270: AWS API MCP Server · Improper Protection of Alternate Path
Affects AWS API MCP ServerSource CVE Database V5
Not known to be exploited · CVSS 5.5 Medium : upgrade to 1.3.9 when convenient.
Data as of 30 Oct 2026, 06:59 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 2% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 1.3.9
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:NExploitation evidence
Disclosed: evidence found.
CVE published 16 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.
What to do
Upgrade AWS API MCP Server and awslabs-aws-api-mcp-server to 1.3.9.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| AWSAWS API MCP Server | Affected
| Fixed in
|
PyPIawslabs-aws-api-mcp-serverpkg:pypi/awslabs-aws-api-mcp-serverOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
A patch is available in AWS API MCP Server version 1.3.9. Users should upgrade to this version to remediate the vulnerability. No additional mitigations are specified or required beyond applying the official fix.
Description
CVE-2026-4270 is a medium severity vulnerability in AWS API MCP Server versions from 0.2.14 up to but not including 1.3.9. It involves improper protection of an alternate path in the no-access and workdir feature, which may allow bypassing intended file access restrictions and expose arbitrary local file contents within the MCP client application context. The issue is fixed in version 1.3.9.