Resource Exhaustion in ag-ui-protocol ag-ui

Executive Summary

CVE-2026-120237 is a flaw in the ag-ui client library (version 0.0.58) where interrupts without an expiresAt field are treated as never expiring. This causes threads to become permanently blocked because the client waits indefinitely for interrupts that cannot auto-clear. The issue stems from the isInterruptExpired function returning false when expiresAt is undefined, with no default time-to-live (TTL).

A server can send a RUN_FINISHED outcome with interrupts missing expiresAt, preventing subsequent runs from completing. The client locks up as no recovery path exists, and the list of pending interrupts grows without bound.

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Detection Guidance

Check for ag-ui client versions up to 0.0.58. Monitor for threads stuck indefinitely due to interrupts without expiresAt fields. Look for RUN_FINISHED outcomes with interrupts lacking expiresAt causing permanent thread bricking.

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Impact Analysis

This vulnerability can cause complete lockup of agent sessions, as threads become permanently blocked waiting for interrupts that never expire. This disrupts AI agent operations, halts real-time interactions, and may require manual intervention to recover. Systems relying on ag-ui for agentic workflows could face downtime or degraded performance.

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Compliance Impact

The vulnerability could lead to denial-of-service conditions by permanently blocking agent threads, potentially disrupting services handling sensitive data. This may impact compliance with GDPR's availability principle or HIPAA's integrity requirements if critical systems become unavailable due to unhandled interrupts.

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Mitigation Strategies

Upgrade ag-ui client to a patched version addressing the issue. Implement default expiry for interrupts missing expiresAt. Limit pending interrupts per thread to prevent unbounded growth.

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