Description

A vulnerability was found in Dvidelabs flatcc up to 0.6.3. This affects the function analyze_struct of the file src/compiler/semantics.c of the component Struct Analysis. The manipulation results in reachable assertion. It is possible to launch the attack remotely. The exploit has been made public and could be used. The patch is identified as f705032346ee39efd7d3848c50b73d455d28d06d. A patch should be applied to remediate this issue.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "5.3",
  "pubDate": "2026-09-14T14:17:19.183Z",
  "pubdate": "2026-09-14T14:17:19.183Z",
  "executiveSummary": "A reachable assertion vulnerability exists in Dvidelabs flatcc versions up to 0.6.3, specifically within the Struct Analysis component.\nThe vulnerability resides in the analyze_struct function located in src/compiler/semantics.c, allowing for potential denial-of-service conditions.\nThis flaw can be triggered remotely, as the compiler is susceptible to malformed inputs that violate internal consistency checks, leading to an assertion failure and subsequent process termination.\nBecause public exploit code is available, the risk of exploitation is elevated for systems utilizing flatcc to process untrusted FlatBuffers schema files.\nSuccessful exploitation requires the attacker to provide a specially crafted schema file to the compiler; no authentication or elevated privileges are required to reach the vulnerable code path.",
  "technicalDetails": "The vulnerability is identified as a reachable assertion failure within the flatcc compiler's semantic analysis phase. The root cause is located in the analyze_struct function within src/compiler/semantics.c, where the compiler performs validation on struct definitions during the schema parsing process.\nAn assertion failure is triggered when the compiler encounters an unexpected state or malformed structure definition that violates a logical precondition defined by the developer. In C, assertions (assert()) are typically used to catch programming errors during development; however, when used in production binaries to validate input data, they become points of failure that can be triggered by external actors.\nThe attack flow commences when an attacker submits a malicious or specifically crafted FlatBuffers schema file to the flatcc compiler. As the compiler parses this file, the execution flow reaches the analyze_struct function. The provided input causes the function to enter a state that fails a critical internal sanity check. Upon this failure, the assert() macro aborts the program execution, causing an immediate denial-of-service for the compilation process.\nSince the compiler is often integrated into automated build pipelines or developer workflows, forcing a crash in the compilation toolchain can disrupt development lifecycles or CI/CD integration. The vulnerability is network-accessible if the compiler is exposed via a web-based service, API, or remote build environment where users can submit schema definitions for compilation.\nThe exploitability is confirmed by the availability of public proof-of-concept material, indicating that the specific input patterns required to bypass initial checks and trigger the assertion are known. Given the nature of flatcc as a compiler, the post-exploitation impact is primarily limited to process termination (Denial of Service), as the crash occurs within the memory space of the compiler process itself, preventing successful compilation of the schema and potentially impacting availability of dependent build tasks.\nThe vulnerability affects all versions of flatcc up to and including 0.6.3. The absence of proper input sanitization before reaching the assertion logic facilitates the triggering of this vulnerability."
}