CVE-2026-102463 in Vert.x
Summary
by MITRE • 10/15/2026
In Eclipse Vert.x versions [4.0.0, 4.5.34] or [5.0.0,5.0.12] or [5.1.0,5.1.9] or [5.2.0, 5.2.0], the binary array decoder in vertx-pg-client (DataTypeCodec.binaryDecodeArray) allocates a Java array sized by a server-declared 32-bit dimension count with no upper bound. A malicious or compromised PostgreSQL server, or an on-path attacker intercepting an unencrypted connection, can send a crafted DataRow message with an excessively large array dimension value, causing the client to attempt a multi-gigabyte heap allocation and crash with an OutOfMemoryError.
The impacted component is io.vertx:vertx-pg-client.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability identified in Eclipse Vert.x versions spanning 4.0.0 through 5.2.0 within the vertx-pg-client module represents a critical resource exhaustion flaw rooted in improper input validation during binary data decoding. Specifically, the DataTypeCodec.binaryDecodeArray method is responsible for parsing array structures transmitted by PostgreSQL servers over the wire protocol. When processing these arrays, the client relies on dimension counts provided directly by the server to determine the size of the Java heap memory required to store the resulting object. The core technical flaw lies in the absence of any upper bound or sanity check applied to this 32-bit integer value before it is used for array instantiation. This design decision assumes that the remote peer will always provide reasonable and safe dimension values, which is a dangerous assumption in security-sensitive contexts where trust boundaries may be crossed by malicious actors or compromised infrastructure.
From an operational perspective, this flaw allows for a severe denial of service attack against any application utilizing the affected Vert.x PostgreSQL client versions. An attacker who can intercept unencrypted connections between the client and server, or one who controls a rogue or compromised PostgreSQL instance, can craft a malformed DataRow message containing an excessively large array dimension value. Upon receiving this crafted payload, the vulnerable code path attempts to allocate a Java array with a size corresponding to that massive integer. Since there is no limit on the allocation size, the JVM will attempt to reserve multi-gigabytes of heap space in a single operation. This action inevitably triggers an OutOfMemoryError, causing the application thread handling the connection to crash and potentially destabilizing the entire Vert.x event loop if not properly isolated. The impact extends beyond simple process termination; it can lead to cascading failures in microservices architectures where such crashes disrupt service availability and degrade overall system reliability.
This vulnerability aligns with CWE-789, which classifies memory allocation without proper limits or bounds checking as a high-severity weakness. By failing to validate the size of incoming data structures against expected application constraints, the software exposes itself to resource exhaustion attacks that are difficult to mitigate through standard network-level controls alone. Furthermore, this behavior can be mapped to ATT&CK technique T1498, Network Denial of Service, specifically under the sub-technique of Resource Exhaustion via Uncontrolled Allocation. The attack vector requires either a compromised server or an on-path attacker capable of modifying traffic in transit for unencrypted connections, highlighting the importance of using encrypted channels such as TLS to prevent interception and manipulation of protocol messages by third parties.
To mitigate this risk, organizations must upgrade their Eclipse Vert.x dependencies to versions outside the affected ranges, specifically ensuring that vertx-pg-client is updated beyond version 5.2.0 or earlier patched releases within the 4.x and 5.x branches where fixes have been backported. In addition to upgrading software components, developers should enforce strict network security policies by mandating encrypted connections for all database communications, thereby preventing on-path attackers from injecting malicious payloads into the data stream. Application-level defenses such as circuit breakers can also help contain the impact of a single crash, though they do not address the root cause. Regular vulnerability scanning and dependency management practices are essential to ensure that libraries like Vert.x remain free from known exploitable flaws in their core protocol handling logic.