How Secure is Secure Code Generation? Adversarial Prompts Put LLM Defenses to the Test

Abstract: Recent secure code generation methods, using vulnerability-aware fine-tuning, prefix-tuning, and prompt optimization, claim to prevent LLMs from producing insecure code. However, their robustness under adversarial conditions remains untested, and current evaluations decouple security from functionality, potentially inflating reported gains. We present the first systematic adversarial audit of state-of-the-art secure code generation methods (SVEN, SafeCoder, PromSec). We subject them to realistic prompt perturbations such as paraphrasing, cue inversion, and context manipulation that developers might inadvertently introduce or adversaries deliberately exploit. To enable fair comparison, we evaluate all methods under consistent conditions, jointly assessing security and functionality using multiple analyzers and executable tests. Our findings reveal critical robustness gaps: static analyzers overestimate security by 7 to 21 times, with 37 to 60% of ``secure'' outputs being non-functional. Under adversarial conditions, true secure-and-functional rates collapse to 3 to 17%. Based on these findings, we propose best practices for building and evaluating robust secure code generation methods. Our code is available.