CVE-2019-11834 in cJSON
Summary
by MITRE
cJSON before 1.7.11 allows out-of-bounds access, related to \x00 in a string literal.
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Analysis
by VulDB Data Team • 07/22/2025
The vulnerability identified as CVE-2019-11834 affects the cJSON library version 1.7.10 and earlier, representing a critical out-of-bounds memory access flaw that can lead to arbitrary code execution or system compromise. This issue stems from improper handling of string literals within the library's parsing routines, specifically when processing malformed JSON input containing null bytes or special character sequences. The vulnerability manifests when the library encounters certain string representations that contain embedded null characters or unusual escape sequences, causing the parser to traverse memory beyond the allocated buffer boundaries. This type of flaw falls under the category of buffer overflow conditions and is classified as CWE-121 in the Common Weakness Enumeration catalog, which specifically addresses stack-based buffer overflow conditions. The issue is particularly dangerous because cJSON is widely used across numerous applications and systems for JSON parsing, making the potential attack surface extensive and impactful.
The technical exploitation of this vulnerability occurs when an attacker supplies malformed JSON data containing null bytes or specially crafted string literals that trigger the out-of-bounds memory access during parsing operations. The library's internal buffer management fails to properly validate string boundaries, allowing memory access beyond the intended allocation limits. This can result in memory corruption that may be exploited to execute arbitrary code or cause denial of service conditions. The flaw is particularly concerning because it can be triggered through standard JSON parsing operations without requiring special privileges or complex attack vectors. When the parser encounters a string literal containing embedded null characters, the memory traversal can extend beyond the allocated buffer space, potentially overwriting adjacent memory locations or causing program crashes. The vulnerability can be categorized under the ATT&CK technique T1059.007 for execution through script-based languages, as it affects applications that rely on cJSON for processing user-supplied JSON data.
The operational impact of CVE-2019-11834 extends across numerous software ecosystems that depend on the cJSON library for JSON processing capabilities. Applications ranging from web servers and IoT devices to mobile applications and enterprise software platforms may be vulnerable to this flaw, creating widespread security implications. The vulnerability can be exploited in scenarios where applications process untrusted JSON input from external sources, such as web APIs, user submissions, or network communications. When exploited, this vulnerability can lead to complete system compromise, data exfiltration, or service disruption. The affected systems may include web applications, embedded devices, network appliances, and middleware components that utilize cJSON for configuration management or data exchange operations. Organizations using vulnerable versions of cJSON must urgently assess their attack surface and implement immediate mitigations to prevent potential exploitation. The vulnerability's impact is amplified by the library's widespread adoption, as many security tools and applications that process JSON data may be affected. This makes the vulnerability particularly dangerous from a threat landscape perspective, as it can be leveraged by attackers to compromise a broad range of systems and applications that depend on this popular JSON parsing library. The recommended mitigation strategy involves upgrading to cJSON version 1.7.11 or later, which includes proper bounds checking and input validation mechanisms that prevent the out-of-bounds memory access condition.