CVE-2026-88341 in YARA
Summary
by MITRE • 09/22/2026
A reachable assertion vulnerability exists in YARA 4.5.8 when loading crafted .yrc compiled rule files. An attacker can provide a malicious file with an invalid arena configuration (num_buffers=0) that triggers an assertion failure in yr_arena_get_ptr(), causing the application to terminate.
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Analysis
by VulDB Data Team • 09/22/2026
The vulnerability identified in YARA versions up to 4.5.8 represents a critical reliability issue stemming from insufficient input validation during the parsing of compiled rule files with the .yrc extension. This specific flaw is categorized as an assertion failure, which technically aligns with CWE-617: Reachable Assertion. The root cause lies in the internal memory management logic handled by the yr_arena_get_ptr function within the YARA engine's arena allocator subsystem. When a user or automated process attempts to load a maliciously crafted .yrc file, the parser processes metadata that includes configuration parameters for the underlying memory arenas used to store rule structures and strings. Specifically, an attacker can construct a payload where the num_buffers field is set to zero while other fields imply valid data structures dependent on those buffers existing.
Upon loading this malformed file, YARA proceeds through its initialization sequence without performing adequate sanity checks on the arena configuration before attempting memory access operations. The yr_arena_get_ptr function expects at least one buffer to be allocated and accessible within the arena structure. However, because the crafted input specifies zero buffers, the internal state becomes inconsistent with the expectations of subsequent pointer retrieval calls. This discrepancy triggers a defensive assertion check designed for debugging purposes rather than production resilience. In many software engineering practices, assertions are intended to catch programming errors during development but may be compiled into release builds depending on configuration settings or simply fail silently in some contexts while crashing in others. In this case, the assertion failure results in an immediate termination of the YARA process, effectively causing a denial of service condition for any system relying on continuous availability of the scanner.
From an operational perspective, this vulnerability impacts systems that integrate YARA as part of their security infrastructure, such as endpoint detection and response solutions, malware analysis sandboxes, or automated threat hunting pipelines. If these services are configured to automatically scan incoming files using compiled rules stored in .yrc format, a single maliciously crafted rule file can cause the scanning service to crash repeatedly. This leads to resource exhaustion if the system attempts automatic restarts without proper health checks, or it results in blind spots where subsequent threats go undetected because the scanner is offline. The impact extends beyond simple availability; in high-throughput environments, such crashes can disrupt logging pipelines and delay incident response efforts by requiring manual intervention to restore service functionality.
This vulnerability maps directly to MITRE ATT&CK technique T1496: Resource Hijacking under the sub-technique of Denial of Service via resource exhaustion or application crash. While not a direct code execution vector, it serves as an effective initial access disruption mechanism that can be leveraged in broader attack chains where availability is a primary target. Attackers may use this flaw to mask other malicious activities by causing security tools to go offline temporarily, thereby reducing the likelihood of detection during critical phases of an intrusion.
Mitigation strategies primarily involve upgrading YARA to version 4.5.9 or later, where developers have implemented robust input validation checks within the arena initialization routines. These updates ensure that configuration parameters such as num_buffers are validated against minimum thresholds before any memory allocation or pointer operations occur. If immediate patching is not feasible, administrators should implement strict file integrity monitoring and whitelist mechanisms to prevent untrusted .yrc files from being loaded by production instances of YARA. Additionally, deploying the scanner behind a wrapper service that monitors process health can help mitigate availability impacts by automatically restarting crashed processes with appropriate rate limiting to prevent rapid restart loops. Regular auditing of rule sources and enforcing strict provenance controls for compiled rules further reduces the attack surface associated with this class of vulnerability.