Description

The graph.UDF in FalkorDB (Redis module) v4.20.1 to v4.20.4 is not registered as a write command, leading to unexpected behavior within the application.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.1",
  "pubDate": "2026-09-21T21:17:15.247Z",
  "pubdate": "2026-09-21T21:17:15.247Z",
  "executiveSummary": "FalkorDB versions 4.20.1 through 4.20.4 exhibit an improper command registration vulnerability regarding the graph.UDF function. In the Redis module architecture, commands must be explicitly registered with appropriate flags to signify their operational nature, particularly distinguishing between read-only and write operations.\nThe vulnerability involves the failure to register graph.UDF as a write command. Consequently, Redis and its underlying replication and security mechanisms fail to treat invocations of this function as state-changing operations. This misclassification impacts the integrity of command filtering, cluster-wide synchronization, and security enforcement policies that rely on the module's declared command metadata.\nThe primary risk implications involve the potential bypass of security controls designed to restrict state-modifying actions, as well as inconsistencies within replicated environments where write operations are expected to be propagated or governed by specific write-locking mechanisms. Attackers capable of executing UDF operations may exploit this misclassification to perform unauthorized state modifications under the guise of read-only activity. Exploitation requires access to the database interface where the module is loaded and operational.",
  "technicalDetails": "The root cause of this vulnerability lies in the Redis module API command registration process within the FalkorDB engine. When a module developer registers a command using RedisModule_CreateCommand, they must supply a string of flags defining the command's behavior (e.g., 'write', 'denyoom', 'admin'). In versions 4.20.1 to 4.20.4, the graph.UDF function lacks the essential 'write' flag, leading the Redis command dispatcher to classify it as a non-mutating (read-only) operation.\nThe attack flow initiates when an authenticated user or application invokes the graph.UDF command. Because the command lacks the 'write' attribute, the Redis server treats it as a query that does not modify the keyspace. This has significant consequences in environments utilizing secondary replicas or read-only replicas, as the command may be incorrectly permitted in contexts where write operations are forbidden or intended to be gated. Furthermore, command auditing or security monitoring tools that filter based on Redis module metadata will fail to flag the execution of this function as a potential change to the database state.\nSpecifically, the vulnerable component is the command registration logic within the FalkorDB core. By failing to specify the 'write' capability, the module misinforms the Redis core regarding the side effects of the UDF execution. If an environment is configured with strict command blacklisting or security policies that deny 'write' commands to specific users or roles, this vulnerability allows for an unauthorized privilege escalation, where the user can execute logic that effectively alters database state while bypassing the intended restriction mechanisms.\nThe post-exploitation impact is multifaceted. Firstly, it undermines the consistency of replicated databases, as the node hosting the primary might undergo changes that are not properly governed by the write-propagation policies of the Redis cluster. Secondly, it provides a vector for bypassing access control lists (ACLs) that rely on the 'write' flag to restrict destructive operations. As the module effectively hides its mutating nature, it invalidates the assumptions of any security layer built on top of the Redis module's command metadata, potentially allowing for unauthorized modification of the underlying graph structures or associated data types managed by FalkorDB."
}