CVE-2010-1224 in Asterisk
Summary
by MITRE
main/acl.c in Asterisk Open Source 1.6.0.x before 1.6.0.25, 1.6.1.x before 1.6.1.17, and 1.6.2.x before 1.6.2.5 does not properly enforce remote host access controls when CIDR notation "/0" is used in permit= and deny= configuration rules, which causes an improper arithmetic shift and might allow remote attackers to bypass ACL rules and access services from unauthorized hosts.
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Analysis
by VulDB Data Team • 05/04/2026
The vulnerability described in CVE-2010-1224 represents a critical access control flaw within the Asterisk Open Source telephony system that affects multiple versions of the software. This issue resides in the main/acl.c file and specifically targets the implementation of Access Control List (ACL) functionality that governs remote host access controls. The vulnerability manifests when CIDR notation with a "/0" prefix is utilized in permit= and deny= configuration directives, creating a dangerous condition that can be exploited by remote attackers to bypass security restrictions. The flaw essentially allows unauthorized hosts to gain access to services that should be restricted based on configured ACL rules, fundamentally undermining the security model of the telephony system.
The technical root cause of this vulnerability stems from improper arithmetic handling within the ACL validation logic when processing CIDR notation. When the system encounters a "/0" CIDR specification, it performs an arithmetic shift operation that fails to correctly evaluate the network address range, resulting in a malformed access control decision. This improper arithmetic shift effectively neutralizes the security controls, as a "/0" prefix should theoretically permit access from any host, but the flawed implementation causes the system to incorrectly interpret the rule, potentially allowing unauthorized access while appearing to enforce legitimate restrictions. This type of flaw falls under CWE-191 Integer Underflow/Overflow, where the improper handling of network address calculations leads to unexpected behavior in access control enforcement. The vulnerability demonstrates a classic case of insufficient input validation and improper boundary condition handling in security-critical code paths.
The operational impact of this vulnerability is severe and far-reaching for organizations relying on Asterisk for their telephony infrastructure. Remote attackers can exploit this flaw to bypass authentication mechanisms and gain unauthorized access to telephony services, potentially leading to eavesdropping on calls, unauthorized calling, toll fraud, and complete system compromise. The vulnerability affects the core functionality of the telephony system, as it undermines the fundamental security controls designed to restrict access to authorized hosts only. Organizations using affected versions of Asterisk may find their communication systems vulnerable to unauthorized access, potentially resulting in significant financial losses, privacy violations, and regulatory compliance issues. The attack surface extends beyond simple access control bypass to include potential escalation paths that could allow attackers to leverage the compromised system for further attacks within the network infrastructure.
Organizations should prioritize immediate remediation by upgrading to patched versions of Asterisk where the ACL handling logic has been corrected to properly process CIDR notation and prevent the arithmetic shift vulnerability. The fix involves implementing proper validation of CIDR prefix lengths and ensuring that arithmetic operations on network addresses maintain correct boundaries when evaluating access control rules. Security administrators should also review existing ACL configurations to identify any instances of "/0" notation that could potentially be exploited, and implement additional monitoring to detect unauthorized access attempts. Network segmentation and additional layers of security controls should be considered as defensive measures while awaiting patch deployment. The vulnerability aligns with ATT&CK technique T1078 Valid Accounts, as it allows attackers to bypass authentication mechanisms and gain access to systems that would otherwise be restricted, potentially enabling further lateral movement within the network infrastructure. Organizations should also consider implementing intrusion detection systems to monitor for patterns consistent with this specific vulnerability exploitation attempt.