CVE-2019-11467 in Couchbase Server
Summary
by MITRE
An issue was discovered in Couchbase Server 4.6.3 and 5.5.0. A JSON document to be stored with more than 3000 '\t' characters can crash the indexing system.
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Analysis
by VulDB Data Team • 12/19/2023
The vulnerability identified as CVE-2019-11467 represents a critical denial of service condition within Couchbase Server versions 4.6.3 and 5.5.0 that specifically targets the indexing subsystem. This flaw manifests when processing JSON documents containing excessive whitespace characters, particularly tab characters, which can cause the database system to become unresponsive or crash entirely. The vulnerability operates through a buffer overflow condition in the indexing engine where the system fails to properly validate input lengths during document processing, creating an exploitable condition that can be leveraged by malicious actors to disrupt database operations.
The technical implementation of this vulnerability stems from inadequate input validation within the Couchbase indexing mechanism. When a JSON document exceeds the threshold of 3000 tab characters, the system's internal parsing routines encounter a condition where memory allocation fails to properly handle the excessive whitespace sequence. This behavior aligns with CWE-129, which describes improper validation of length of input data, and CWE-131, which covers improper handling of length parameters in input operations. The indexing system's failure to implement proper bounds checking on document size parameters creates a pathway for memory corruption that ultimately results in system instability and service disruption.
The operational impact of this vulnerability extends beyond simple system crashes to encompass broader database availability concerns that can severely affect enterprise applications relying on Couchbase for data storage and retrieval. Organizations utilizing affected versions may experience unexpected downtime, data access failures, and potential loss of service for applications dependent on the database's indexing capabilities. The vulnerability's exploitation requires minimal effort from an attacker since it only necessitates crafting a document with sufficient tab characters, making it particularly dangerous in environments where untrusted data is processed. This characteristic places the vulnerability in the ATT&CK framework under the T1499.004 technique for network denial of service, as it specifically targets system availability through resource exhaustion mechanisms.
Mitigation strategies for CVE-2019-11467 require immediate implementation of version upgrades to patched Couchbase Server releases that address the indexing validation flaw. Organizations should also implement input sanitization measures at application layers to validate and limit document sizes before processing, particularly for documents containing excessive whitespace characters. Network-level protections such as rate limiting and content filtering can help reduce the attack surface by preventing malformed documents from reaching the indexing system. Additionally, implementing monitoring solutions that detect unusual patterns in document processing or system resource consumption can provide early warning of potential exploitation attempts. Regular security assessments and vulnerability scanning should be conducted to identify similar conditions in other database components, as this vulnerability demonstrates the importance of proper input validation in preventing system instability.