CVE-2011-2529 in Asterisk
Summary
by MITRE
chan_sip.c in the SIP channel driver in Asterisk Open Source 1.6.x before 1.6.2.18.1 and 1.8.x before 1.8.4.3 does not properly handle \0 characters in SIP packets, which allows remote attackers to cause a denial of service (memory corruption) or possibly have unspecified other impact via a crafted packet.
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Analysis
by VulDB Data Team • 11/14/2021
The vulnerability identified as CVE-2011-2529 resides within the chan_sip.c component of Asterisk Open Source messaging systems, specifically affecting versions prior to 1.6.2.18.1 and 1.8.4.3. This flaw represents a critical security issue that demonstrates poor input validation and memory handling within the SIP channel driver responsible for managing Session Initiation Protocol communications. The vulnerability manifests when the system processes SIP packets containing null characters, which are not properly sanitized or handled during packet parsing operations.
The technical exploitation of this vulnerability occurs through the improper handling of null byte characters within SIP packet structures, creating a memory corruption scenario that can lead to system instability and potential denial of service conditions. When a malicious actor crafts a SIP packet containing null characters and transmits it to an affected Asterisk system, the SIP channel driver fails to adequately process these special characters, leading to buffer overflows or memory corruption issues within the application's memory management subsystem. This weakness directly relates to CWE-121, which addresses stack-based buffer overflow conditions, and CWE-122, covering heap-based buffer overflow scenarios that can occur during dynamic memory allocation.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it can potentially allow remote attackers to execute arbitrary code or cause unpredictable system behavior through carefully crafted SIP packets. Attackers can leverage this vulnerability to disrupt communication services by causing the Asterisk system to crash or become unresponsive, effectively rendering the VoIP infrastructure unavailable to legitimate users. The memory corruption aspects of this vulnerability can also potentially lead to information disclosure or privilege escalation scenarios, depending on the specific system configuration and execution environment.
Mitigation strategies for CVE-2011-2529 should prioritize immediate patching of affected Asterisk installations to versions 1.6.2.18.1 or 1.8.4.3, which contain the necessary fixes for proper null character handling within SIP packet processing. Network administrators should implement additional security measures including SIP packet filtering to prevent malformed packets from reaching the Asterisk system, and establish monitoring protocols to detect unusual SIP traffic patterns that may indicate exploitation attempts. The vulnerability aligns with ATT&CK technique T1190, which covers exploitation of remote services through malformed input handling, and represents a classic example of how insufficient input validation can lead to critical system compromise. Organizations should also consider implementing network segmentation and access controls to limit exposure of their SIP infrastructure to untrusted networks, while maintaining regular security assessments to identify and remediate similar vulnerabilities in their telephony systems.