CVE-2026-114386

Received Received - Intake

Pydantic AI Harness Nested Tool Call Limit Bypass

Publication date: 2026-10-21

Last updated on: 2026-10-21

Assigner: VulnCheck

Description

Pydantic AI Harness before 0.59.0 fails to enforce UsageLimits.tool_calls_limit on nested tool calls dispatched from run_code in the CodeMode toolset. Users or prompt-injected content can make the sandboxed program invoke tools via run_nested_call() without check_before_tool_call, exceeding operator limits on costly or side-effecting tools.

CVSS Scores

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Meta Information

Published

2026-10-21

Last Modified

2026-10-21

Generated

2026-11-10

AI Q&A

2026-10-22

EPSS Evaluated

2026-11-09

NVD

CVE-2026-114386

EUVD

EUVD-2026-107233

Affected Vendors & Products

Vendor	Product	Version / Range
pydantic	pydantic-ai-harness	0

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-770	The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

Attack-Flow Graph

Executive Summary

Pydantic AI Harness before version 0.59.0 fails to enforce the UsageLimits.tool_calls_limit on nested tool calls initiated via the run_code function in the CodeMode toolset. This allows users or prompt-injected content to bypass the limit by invoking tools through run_nested_call() without proper checks, potentially exceeding operator-imposed limits on costly or side-effecting tools.

Detection Guidance

To detect this vulnerability, check the version of Pydantic AI Harness installed on your system. Run: pip show pydantic-ai-harness. If the version is below 0.59.0, the system is vulnerable. Additionally, monitor logs for UsageLimitExceeded errors during nested tool calls in CodeMode.

Impact Analysis

This vulnerability could allow attackers to execute an excessive number of nested tool calls, leading to resource exhaustion, increased costs, or unintended side effects. It may also cause denial-of-service conditions by overwhelming system resources or bypassing intended usage limits.

Compliance Impact

This vulnerability could lead to excessive tool calls bypassing intended limits, potentially causing resource exhaustion or unintended side effects. For GDPR, this may impact data processing integrity and security controls. For HIPAA, it could risk unauthorized access or disclosure of protected health information due to uncontrolled tool execution.

Mitigation Strategies

Upgrade Pydantic AI Harness to version 0.59.0 or later to enforce tool_calls_limit on nested tool calls. Review and adjust tool_calls_limit values to account for nested calls if already set.

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0/70

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