CVE-2014-2744 in Metronome
Summary
by MITRE
plugins/mod_compression.lua in (1) Prosody before 0.9.4 and (2) Lightwitch Metronome through 3.4 negotiates stream compression while a session is unauthenticated, which allows remote attackers to cause a denial of service (resource consumption) via compressed XML elements in an XMPP stream, aka an "xmppbomb" attack.
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Analysis
by VulDB Data Team • 05/10/2026
The vulnerability identified as CVE-2014-2744 represents a critical security flaw in XMPP (Extensible Messaging and Presence Protocol) implementations that affects both Prosody versions prior to 0.9.4 and Lightwitch Metronome versions through 3.4. This vulnerability stems from the improper handling of stream compression negotiation within the XMPP protocol stack, specifically within the mod_compression.lua plugin that manages compression functionality. The flaw allows unauthenticated attackers to exploit the compression mechanism during the initial session establishment phase, creating a significant vector for resource exhaustion attacks.
The technical exploitation of this vulnerability occurs when an attacker establishes an XMPP connection to a vulnerable server and initiates the stream compression negotiation process before authentication is completed. This timing issue enables the attacker to send compressed XML elements that appear benign but consume substantial server resources during decompression. The compressed data can contain nested or recursive XML structures that expand significantly during decompression, leading to exponential resource consumption. The vulnerability operates at the protocol level where the compression negotiation should only occur after successful authentication, but the flawed implementation allows this process to begin prematurely, creating an attack surface that can be leveraged for denial of service.
From an operational perspective, this vulnerability enables what is commonly referred to as an "xmppbomb" attack pattern that can effectively exhaust server resources including memory, CPU cycles, and network bandwidth. The attack mechanism exploits the fundamental assumption that compression algorithms should only be applied to authenticated sessions where the server can better control resource allocation. When compression is negotiated during unauthenticated sessions, the server processes compressed XML elements without proper rate limiting or resource constraints, allowing attackers to consume resources proportional to the compressed data size rather than the actual network transmission. This creates a scenario where a small amount of transmitted data can result in massive resource consumption, making it particularly effective for distributed denial of service attacks.
The impact of this vulnerability extends beyond simple service disruption to potentially compromise the entire XMPP infrastructure. Servers that process thousands of concurrent connections become particularly vulnerable as the resource exhaustion can cascade through the system, affecting legitimate users and potentially causing complete service outages. The vulnerability is classified under CWE-20 as "Improper Input Validation" and aligns with ATT&CK technique T1499.100 as "Network Denial of Service" where attackers exploit protocol implementation flaws to exhaust system resources. Organizations using XMPP-based communication systems, particularly those in enterprise environments or service providers, face significant risk as this vulnerability can be exploited by anyone with network access to the XMPP server, making it particularly dangerous in public or shared network environments.
Mitigation strategies for this vulnerability require immediate patching of affected software versions to ensure proper authentication before compression negotiation occurs. System administrators should implement rate limiting and resource monitoring to detect abnormal compression patterns, while also configuring firewalls and network access controls to limit XMPP traffic from untrusted sources. The fix involves modifying the mod_compression.lua plugin to enforce authentication requirements before initiating compression negotiation, typically by requiring a successful SASL authentication process before allowing the stream compression mechanism to be activated. Additionally, organizations should consider implementing connection throttling mechanisms and monitoring for unusual XML element expansion ratios that could indicate exploitation attempts. Network segmentation and proper access controls can also help limit the impact of potential attacks by restricting which systems can initiate XMPP connections to vulnerable servers.