Description

A vulnerability was determined in Dvidelabs flatcc up to 0.6.3. This impacts the function align_order_members of the file src/compiler/semantics.c of the component Duplicate Symbol Handler. This manipulation causes reachable assertion. The attack can be initiated remotely. The exploit has been publicly disclosed and may be utilized. Patch name: 8b19ba4e992ebcad7f5970704d1afc5507fa5205. To fix this issue, it is recommended to deploy a patch.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "5.3",
  "pubDate": "2026-09-14T14:17:19.353Z",
  "pubdate": "2026-09-14T14:17:19.353Z",
  "executiveSummary": "A reachable assertion vulnerability exists in the Duplicate Symbol Handler component of Dvidelabs flatcc versions up to 0.6.3. The vulnerability, located in the align_order_members function within src/compiler/semantics.c, allows a remote attacker to trigger an assertion failure, leading to a denial of service (DoS) condition.\nThe flaw originates from improper handling of specific schema inputs that violate internal consistency expectations within the compiler's semantic analysis phase. By providing a maliciously crafted input, an attacker can force the application to terminate unexpectedly, effectively crashing the compiler process.\nThis vulnerability is particularly significant for environments that rely on flatcc for automated schema compilation or integration into continuous integration pipelines, as it allows for the disruption of build processes. The vulnerability has been publicly disclosed, increasing the risk of active exploitation. The patch 8b19ba4e992ebcad7f5970704d1afc5507fa5205 is available to resolve the underlying logic error, and immediate deployment is recommended to ensure the robustness and availability of the compiler toolchain.",
  "technicalDetails": "The vulnerability resides in the semantic analysis module of the flatcc compiler, specifically within the align_order_members function in src/compiler/semantics.c. The function is responsible for ordering structure members to ensure proper data alignment during the code generation process. An assertion failure is triggered when the input schema violates implicit assumptions regarding member ordering or memory alignment constraints that the compiler expects during the semantic analysis of FlatBuffers schemas.\nThe root cause is a deficiency in input validation during the construction of internal metadata structures within the Duplicate Symbol Handler. When the compiler encounters an ambiguous or specifically malformed combination of symbols, the logic within align_order_members attempts to perform a memory alignment calculation that triggers a programmed assertion (assert()).\nAn attacker can exploit this remotely by submitting a crafted FlatBuffers schema file that triggers the problematic code path. The attack flow proceeds as follows: First, the attacker provides a malicious schema input to the flatcc compiler. During the compilation process, the compiler traverses the schema symbols and reaches the semantic analysis phase. The Duplicate Symbol Handler invokes align_order_members to process member alignments. The function encounters state data that fails to satisfy the condition defined within the assertion, leading to a program abort and immediate termination of the process.\nThis vulnerability does not require authentication or specific privilege levels, provided the target compiler instance is accessible via a network interface or exposed via a build service or web interface that parses untrusted schema input. The primary impact is denial of service, as the termination prevents the successful generation of serialized code. Because this occurs at the compiler level, it effectively halts any downstream development or automated processes dependent on the flatcc toolchain. No further payload execution is currently documented, as the primary mechanism is a process crash, but the ease of triggering this via remote input makes it a significant stability risk for affected systems. The flaw is addressed by patch 8b19ba4e992ebcad7f5970704d1afc5507fa5205, which modifies the logic in align_order_members to handle unexpected symbol alignments gracefully instead of invoking a hard assertion."
}