CVE-2018-7284 in Asterisk
Summary
by MITRE
A Buffer Overflow issue was discovered in Asterisk through 13.19.1, 14.x through 14.7.5, and 15.x through 15.2.1, and Certified Asterisk through 13.18-cert2. When processing a SUBSCRIBE request, the res_pjsip_pubsub module stores the accepted formats present in the Accept headers of the request. This code did not limit the number of headers it processed, despite having a fixed limit of 32. If more than 32 Accept headers were present, the code would write outside of its memory and cause a crash.
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Analysis
by VulDB Data Team • 11/25/2024
The vulnerability identified as CVE-2018-7284 represents a critical buffer overflow condition within the Asterisk telephony platform that affects multiple version ranges including 13.19.1 and earlier, 14.x through 14.7.5, 15.x through 15.2.1, and Certified Asterisk through 13.18-cert2. This issue resides within the res_pjsip_pubsub module which handles SIP subscription requests, specifically when processing the Accept headers present in SUBSCRIBE requests. The flaw demonstrates a classic memory corruption vulnerability where the software fails to properly validate input parameters against predetermined limits. The module maintains a fixed buffer size of 32 entries for storing accepted formats but lacks proper enforcement mechanisms to prevent overflow conditions when excessive headers are encountered. This discrepancy between the intended limit and actual processing behavior creates a scenario where malicious actors can craft specially crafted SIP requests to trigger memory corruption.
The technical implementation of this vulnerability stems from inadequate bounds checking within the SIP processing pipeline. When the res_pjsip_pubsub module processes incoming SUBSCRIBE requests, it iterates through the Accept headers without proper validation of header count against the predetermined 32-entry limit. Each Accept header is stored in a fixed-size array or buffer structure, and when the number of headers exceeds 32, the code continues writing beyond the allocated memory boundaries. This memory corruption manifests as a buffer overflow condition that can result in application instability, denial of service, or potentially more severe consequences depending on the execution environment. The vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and represents a failure in input validation and memory management practices. From an operational perspective, this vulnerability directly impacts the availability and reliability of SIP-based telephony services, as a single malicious request can cause the Asterisk service to crash and restart, disrupting voice communication channels.
The operational impact of CVE-2018-7284 extends beyond simple service disruption to encompass broader security implications within telecommunications infrastructure. Organizations relying on Asterisk for voice services face potential denial of service attacks that can render their communication systems unavailable to legitimate users. The vulnerability is particularly concerning in enterprise environments where Asterisk serves as a core component of unified communications platforms, as it can be exploited by attackers to create persistent service interruptions. The attack vector requires minimal sophistication, as an attacker only needs to craft a SIP SUBSCRIBE request with more than 32 Accept headers to trigger the overflow condition. This makes the vulnerability highly exploitable in environments where SIP traffic is not properly filtered or monitored. The potential for remote code execution cannot be entirely ruled out in certain configurations, particularly when considering the broader ATT&CK framework's approach to privilege escalation and system compromise through memory corruption vulnerabilities. Organizations implementing SIP-based communication systems should prioritize patching this vulnerability, as it represents a significant risk to business continuity and service availability. The vulnerability also highlights the importance of proper input validation and memory management practices in telephony software implementations, particularly in mission-critical communication infrastructure where reliability and security are paramount considerations.