CAPEv2 Denial-of-Analysis Vulnerability Allowing Incomplete Behavioral Reports

A denial-of-analysis vulnerability has been identified in CAPEv2, specifically in the reporting/mongodb.py and reporting/jsondump.py files. This issue, present in commit 52e4b43 dated May 17, 2025, allows attackers who can submit samples to disrupt the behavioral analysis process. By generating deeply nested or oversized behavior data, these attackers can trigger MongoDB BSON limits or cause recursion errors with the orjson library, leading to incomplete or missing analysis reports. The vulnerability arises from CAPEv2's handling of complex behavior data during dynamic malware analysis, where excessive nesting or size can cause the database to reject reports or the JSON serializer to fail, aborting report generation.

Impact

Exploitation of this vulnerability causes the dynamic analysis engine to miss capturing or reporting behavioral activity, allowing malware to evade detection and appear benign in analysis results.

Reproduction

The vulnerability can be reproduced by submitting samples that generate large, complex behavior reports exceeding MongoDB's 16 MB BSON document size limit or maximum nesting depth of 100 levels. This can be done by using payloads that create extensive process trees or recursive data. During the analysis, CAPEv2 may log MongoDB OperationFailure Code 15 errors or 'Recursion limit reached' warnings, indicating that the report generation has failed. As a result, the final analysis report may show no behavioral data or indicate a failed reporting status, creating the false impression that the malware was inactive or harmless.