CVE-2026-18830Network attack vector

Authenticated tool execution via caller-supplied content block

Published Aug 4, 2026 · Updated Aug 4, 2026

Improper input validation in Amazon Bedrock AgentCore harness before July 31, 2026 allows remote authenticated users to execute configured tools. The InvokeHarness agent event loop dispatches a tool named in a caller-supplied tool-use content block in the final message without model mediation. Access requires authenticated InvokeHarness permissions, and execution is limited to tools configured on that harness; a harness without tools has no tool-execution impact.

CVSS severity8.6
High
EPSS probability0.53%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Amazon Bedrock AgentCore harness before July 31, 2026 allows remote authenticated users to execute configured tools. The InvokeHarness agent event loop dispatches a tool named in a caller-supplied tool-use content block in the final message without model mediation. Access requires authenticated InvokeHarness permissions, and execution is limited to tools configured on that harness; a harness without tools has no tool-execution impact.

The record

CVE
CVE-2026-18830
Published
Aug 4, 2026
Updated
Aug 4, 2026
Vendor
Amazon Web Services
Product
Amazon Bedrock AgentCore harness
Classifications
CWE-1287
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 4, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=N/A

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Amazon Web Services · Amazon Bedrock AgentCore harnessversion=N/A

Published CVSS scores

8.1Amazon Web ServicesCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
8.6Amazon Web ServicesCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1287Improper Validation of Specified Type of Input

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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