CVE-2011-2532 in Prosody
Summary
by MITRE
The json.decode function in util/json.lua in Prosody 0.8.x before 0.8.1 might allow remote attackers to cause a denial of service (infinite loop) via invalid JSON data, as demonstrated by truncated data.
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Analysis
by VulDB Data Team • 02/09/2019
The vulnerability identified as CVE-2011-2532 represents a critical denial of service flaw in the Prosody XMPP server software version 0.8.x prior to 0.8.1. This issue specifically affects the json.decode function located within the util/json.lua module, which serves as a core component for processing JSON data within the messaging platform. The vulnerability stems from inadequate input validation and error handling mechanisms that fail to properly process malformed or truncated JSON sequences, creating a condition where malicious actors can exploit the system's parsing logic to trigger unintended behavior.
The technical implementation of this vulnerability occurs when the json.decode function encounters invalid JSON data that has been specifically crafted to exploit parsing state machine transitions. When the function processes truncated or malformed JSON input, it enters an infinite loop due to improper boundary checking and state management within the parsing algorithm. This occurs because the function does not adequately validate the structure of incoming JSON data before attempting to parse it, allowing malformed sequences to cause the parser to continuously iterate through internal state transitions without making progress toward completion. The flaw is particularly insidious as it can be triggered by simply sending malformed JSON data to any service that utilizes the affected Prosody version's JSON parsing capabilities.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the availability and stability of XMPP services that rely on Prosody 0.8.x before 0.8.1. Remote attackers can exploit this weakness to consume excessive system resources through CPU-bound infinite loops, effectively rendering the targeted service unavailable to legitimate users. This denial of service condition can be particularly damaging in production environments where continuous availability is critical for communication services, as it can lead to complete service outages that affect numerous users and applications depending on the XMPP infrastructure. The vulnerability affects any application or service component that utilizes the affected json.decode function, making it a widespread concern across systems leveraging this version of Prosody.
Security practitioners should implement immediate mitigations including upgrading to Prosody version 0.8.1 or later, which contains the necessary patches to address the infinite loop condition in the JSON parsing logic. Organizations should also consider implementing input validation mechanisms at network boundaries to filter malformed JSON data before it reaches the vulnerable components. Additionally, monitoring systems should be configured to detect unusual CPU usage patterns that may indicate exploitation attempts. From a compliance perspective, this vulnerability aligns with CWE-835, which addresses infinite loops in software, and can be categorized under ATT&CK technique T1499.004 for network denial of service attacks. The remediation process should include thorough testing of the patched version to ensure that legitimate JSON parsing functionality remains intact while eliminating the infinite loop conditions that enable the denial of service attack vector.