CVE-2022-31001 in Sofia-SIP
Summary
by MITRE • 06/01/2022
Sofia-SIP is an open-source Session Initiation Protocol (SIP) User-Agent library. Prior to version 1.13.8, an attacker can send a message with evil sdp to FreeSWITCH, which may cause crash. This type of crash may be caused by `#define MATCH(s, m) (strncmp(s, m, n = sizeof(m) - 1) == 0)`, which will make `n` bigger and trigger out-of-bound access when `IS_NON_WS(s[n])`. Version 1.13.8 contains a patch for this issue.
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Analysis
by VulDB Data Team • 06/04/2022
The vulnerability CVE-2022-31001 affects Sofia-SIP, a widely-used open-source Session Initiation Protocol User-Agent library that serves as the foundation for many VoIP implementations including FreeSWITCH. This issue represents a classic buffer overflow vulnerability that can be exploited through malformed Session Description Protocol (SDP) messages. The flaw exists in the way the library processes SDP content during SIP message handling, specifically within the string matching mechanism that determines protocol compliance. The vulnerability is particularly concerning because it can be triggered remotely by sending specially crafted SIP messages to systems using vulnerable versions of Sofia-SIP, making it a potential denial-of-service vector that could disrupt VoIP communications.
The technical root cause of this vulnerability lies in the MATCH macro implementation which uses strncmp for string comparison but fails to properly handle boundary conditions. The problematic code structure defines n as the length of the comparison string minus one, but when processing certain malformed SDP content, this calculation can result in n being set to a value that exceeds the bounds of the input string. This leads to out-of-bounds memory access when the IS_NON_WS macro attempts to evaluate s[n], causing the application to crash. The vulnerability maps to CWE-121 Stack-based Buffer Overflow and CWE-125 Out-of-bounds Read, demonstrating how improper boundary checking can lead to memory corruption. The specific implementation flaw in the Sofia-SIP library creates a scenario where an attacker can manipulate the value of n through crafted SDP content to trigger memory access violations that result in application termination.
The operational impact of CVE-2022-31001 extends beyond simple service disruption as it affects critical communication infrastructure that relies on SIP for voice and video conferencing. Systems running vulnerable versions of Sofia-SIP, particularly those using FreeSWITCH as their PBX platform, become susceptible to remote crashes that can be exploited by malicious actors to interrupt business communications. The vulnerability is particularly dangerous in enterprise environments where VoIP systems handle critical business communications, as the crash can occur without any authentication requirements, making it an attractive target for attackers seeking to disrupt operations. From an ATT&CK framework perspective, this vulnerability aligns with T1499.004 Network Denial of Service and T1595.001 Active Scanning, as it enables remote exploitation of network services through crafted protocol messages. The impact is amplified because SIP-based systems often serve as core communication infrastructure, making successful exploitation potentially devastating for organizations relying on these services.
The patch released in version 1.13.8 addresses the vulnerability by implementing proper boundary checking and input validation within the SDP parsing logic. Organizations should prioritize updating their Sofia-SIP installations to version 1.13.8 or later to remediate this vulnerability. System administrators should also implement network monitoring to detect unusual SIP traffic patterns that might indicate exploitation attempts. Additional mitigations include implementing proper input sanitization at network boundaries, deploying intrusion detection systems that can identify malformed SDP content, and conducting regular security assessments of VoIP infrastructure. The vulnerability highlights the importance of robust input validation in telecommunications protocols and serves as a reminder that even widely-used open-source libraries can contain critical flaws that require continuous security monitoring and patch management processes.