What percentage of LLM-generated C/C++ code has vulnerabilities?

55.8% overall, with GPT-4o at 62.4%. Formal verification via Z3 confirmed 1,055 exploits.

Do static analysis tools catch LLM C/C++ flaws?

No—97.8% miss rate on CodeQL, Semgrep, etc. They can't handle novel invariant breaks.

Can LLM self-review fix its own insecure code?

It spots 78.7% of bugs but fails to prevent them during generation. Retraining needed.

LLMs Pump Out Vulnerable C/C++ Code—Self-Review Does Nothing to Stop It

Everyone figured LLMs would crank out solid code, maybe even catch their own mistakes. Nope—55.8% of their C/C++ output is a security nightmare, invisible to standard checkers.

theAIcatchup Apr 08, 2026 3 min read

Chart of vulnerability rates in C/C++ code from GPT-4o, Claude, and other LLMs

⚡ Key Takeaways

55.8% of LLM-generated C/C++ code contains verifiable security vulnerabilities, worst in GPT-4o at 62.4%. 𝕏
Standard tools like CodeQL miss 97.8% of these flaws; only formal verification like Z3 catches them. 𝕏
Self-review identifies bugs but doesn't stop insecure code generation—rooted in flawed training data. 𝕏

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#C/C++ vulnerabilities #LLM code generation #Z3 solver #formal verification

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Originally reported by dev.to

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