# CVE-2026-84887: simular-ai Agent-S denial of service in action parameter handling

Source: https://junglewise.ai/threats/cve-2026-84887-simular-ai-agent-s-denial-of-service-in-action-parameter-handling  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-03. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-84887 · Severity: medium · CVSS 4.3 · Published 2026-09-03

Agent-S is an AI-powered automation tool that generates and executes GUI actions based on model output. An attacker can craft prompts that cause the model to generate actions with unbounded parameters (such as extremely long wait times), causing the agent worker to hang indefinitely and become unavailable for legitimate tasks. This could disrupt service availability in any deployment using Agent-S for automated workflows.

Technologies: [Simular-Ai Agent-S](https://junglewise.ai/threats/technologies/agent-s). Vendors: [Simular-Ai](https://junglewise.ai/threats/vendors/simular-ai).

## Quick answers

**Is CVE-2026-84887 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-84887 being exploited in the wild.

**How severe is CVE-2026-84887?** Medium severity, with a CVSS score of 4.3, published 3 September 2026.

**Which products and versions are affected?** Simular-Ai Agent-S up to 0.3.2.

**Is there a fix for CVE-2026-84887?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-84887 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-84887?** Check whether you run Simular-Ai Agent-S at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is a denial-of-service flaw in the model-generated GUI action execution workflow (grounding.py and related modules). Agent-S accepts model-generated action strings, validates only syntactic correctness, then converts and executes them using eval() and exec() without enforcing resource boundaries on action parameters. An attacker can supply a crafted task prompt that causes the local model to return actions like agent.wait(3600) with arbitrary durations. The vulnerable code directly embeds these unsanitized parameters into executable code (e.g., time.sleep(3600)), causing the worker process to block for attacker-controlled durations. No per-action runtime budget or parameter validation exists before execution, allowing a single malicious prompt to monopolize the worker and cause subsequent legitimate tasks to time out or remain pending. The vendor was contacted early but did not respond.

## Affected products

- simular-ai Agent-S up to 0.3.2

## Timeline

- 2026-09-03: disclosed
- other: Exploit code publicly available on GitHub

## References

- [https://github.com/outlookgp/CVE/tree/main/AgentS_Action_Parameter_Budget_DoS_Report](https://github.com/outlookgp/CVE/tree/main/AgentS_Action_Parameter_Budget_DoS_Report)
- [https://vuldb.com/cve/CVE-2026-84887](https://vuldb.com/cve/CVE-2026-84887)

## Related threats

- [simular-ai Agent-S denial of service in OCR HTTP API](https://junglewise.ai/threats/cve-2026-84886-simular-ai-agent-s-denial-of-service-in-ocr-http-api)
- [simular-ai Agent-S denial of service in CodeAgent](https://junglewise.ai/threats/cve-2026-84885-simular-ai-agent-s-denial-of-service-in-codeagent)