用形式化验证提前发现前沿模型沙盒的算术漏洞，提升安全防护能力。
Mythos and the Unverified Cage: Z3-Based Pre-Deployment Verification for Frontier-Model Sandbox Infrastructure
- 基于Z3的SMT求解器，自动检测C/C++代码中的算术漏洞模式。
- 在四个真实生产项目中验证有效，生成可复现的证明与反例。
- 提出四层防护框架，适合关注模型安全与系统可信的开发者。
2026年4月，Claude Mythos沙盒逃逸事件暴露了前沿人工智能隔离基础设施的关键缺陷：其底层代码仍存在可形式化描述的算术漏洞。尽管Anthropic未公开具体逃逸路径，但有次级分析推测为沙盒网络代码中的CWE-190算术溢出漏洞。本文不依赖未证实假设，转而研究该漏洞类别本身。提出COBALT——一个基于Z3 SMT的正式验证引擎，用于在部署前识别C/C++基础设施中CWE-190/191/195类算术漏洞模式。验证层面：在NASA cFE、wolfSSL、Eclipse Mosquitto和NASA F Prime四个生产代码库上成功检测出漏洞，产出可验证的SAT结果（含具体反例）与UNSAT保证（在明确安全边界下）。提议层面：构建四层防护框架，包括COBALT、VERDICT、DIRECTIVE-4和SENTINEL，分别对应部署前验证、执行前约束、输出控制与运行时监控，映射到Mythos事件暴露的失效模式。在合理假设下，论证公开报告的Mythos逃逸模式可被Z3形式化表达，并表明前置形式化分析足以揭示该模式。核心观点是：前沿模型安全不能仅依赖行为管控，其隔离栈本身必须接受形式化验证。
原文摘要 · Abstract (English)
The April 2026 Claude Mythos sandbox escape exposed a critical weakness in frontier AI containment: the infrastructure surrounding advanced models remains susceptible to formally characterizable arithmetic vulnerabilities. Anthropic has not publicly characterized the escape vector; some secondary accounts hypothesize a CWE-190 arithmetic vulnerability in sandbox networking code. We treat this as unverified and analyze the vulnerability class rather than the specific escape. This paper presents COBALT, a Z3 SMT-based formal verification engine for identifying CWE-190/191/195 arithmetic vulnerability patterns in C/C++ infrastructure prior to deployment. We distinguish two classes of contribution. Validated: COBALT detects arithmetic vulnerability patterns in production codebases, producing SAT verdicts with concrete witnesses and UNSAT guarantees under explicit safety bounds. We demonstrate this on four production case studies: NASA cFE, wolfSSL, Eclipse Mosquitto, and NASA F Prime, with reproducible encodings, verified solver output, and acknowledged security outcomes. Proposed: a four-layer containment framework consisting of COBALT, VERDICT, DIRECTIVE-4, and SENTINEL, mapping pre-deployment verification, pre-execution constraints, output control, and runtime monitoring to the failure modes exposed by the Mythos incident. Under explicit assumptions, we further argue that the publicly reported Mythos escape class is consistent with a Z3-expressible CWE-190 arithmetic formulation and that pre-deployment formal analysis would have been capable of surfacing the relevant pattern. The broader claim is infrastructural: frontier-model safety cannot depend on behavioral safeguards alone; the containment stack itself must be subjected to formal verification.
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