CVE-2026-88409 in FalkorDB
Summary
by MITRE • 09/22/2026
FalkorDB (Redis module) v4.20.1 to v4.20.4 was discovered to contain a buffer overflow in the _Decode_GrB_Matrix function (/v19/decode_matrix.c). This vulnerability allows attackers to cause a Denial of Service (DoS) via a crafted input.
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Analysis
by VulDB Data Team • 09/22/2026
FalkorDB, an open-source graph database module for Redis, experienced a critical security flaw in versions ranging from v4.20.1 through v4.20.4 involving improper memory handling within its matrix decoding subsystem. The vulnerability is specifically located in the _Decode_GrB_Matrix function found in the source file decode_matrix.c of version 19. This component is responsible for parsing and interpreting serialized graph matrix data structures that are passed into the database engine during query execution or data ingestion processes. When FalkorDB receives input intended to construct a GraphBLAS-compatible matrix, it relies on this decoding routine to validate dimensions, allocate appropriate memory buffers, and populate internal data structures with the provided values. The flaw arises because the function fails to adequately verify the bounds of incoming array indices against the allocated buffer size before performing write operations.
The technical nature of this vulnerability is classified as a heap-based buffer overflow under CWE-122. During the decoding process, if an attacker provides a crafted input where the declared dimensions or index values exceed the actual capacity of the pre-allocated memory region, the function proceeds to write data beyond the boundaries of the allocated block. This out-of-bounds write corrupts adjacent memory structures on the heap, which may include metadata used by the allocator, pointers to other objects, or control flow information within the FalkorDB process space. Because this operation occurs during the processing of user-supplied input, it represents a classic case of insufficient validation leading to memory corruption. The severity is compounded by the fact that Redis modules operate with significant privileges and direct access to system resources, making any instability in their execution highly disruptive.
The operational impact of exploiting this buffer overflow primarily manifests as a Denial of Service condition for FalkorDB instances running affected versions. When the heap metadata or critical internal pointers are corrupted due to the out-of-bounds write, the Redis server process typically encounters an illegal memory access error and crashes immediately. This results in the abrupt termination of the database service, causing downtime for all connected clients and potentially leading to data loss if transactions were being processed at the moment of failure. While some buffer overflows can lead to remote code execution, in this specific context within FalkorDB's architecture, the primary observed consequence is process instability and unavailability rather than arbitrary command execution. However, the potential for more severe exploitation cannot be entirely ruled out depending on the exact memory layout and heap allocator behavior of the underlying system environment.
From a threat intelligence perspective, this vulnerability aligns with ATT&CK technique T1498 Network Denial of Service, as it enables an attacker to disrupt service availability through resource exhaustion or process termination via crafted network packets containing malicious matrix data. It also relates to CWE-20 Improper Input Validation, highlighting the failure to sanitize and validate external inputs before processing them within sensitive memory operations. The vulnerability affects a specific range of versions, indicating that earlier releases prior to v4.20.1 were not susceptible, while later patches beyond v4.20.4 likely addressed this issue through improved bounds checking or stricter input validation protocols in the decode_matrix.c module.
To mitigate this risk, organizations running FalkorDB must immediately upgrade to a version newer than v4.20.4 where the buffer overflow has been patched. If upgrading is not immediately feasible, administrators should implement strict network-level access controls to restrict who can send queries or data payloads to the Redis port hosting the FalkorDB module. Additionally, deploying Web Application Firewalls with deep packet inspection capabilities may help identify and block malformed matrix structures that exhibit characteristics of this exploit vector. Regular security audits focusing on input validation practices in custom modules are also recommended to prevent similar memory safety issues in future development cycles.