CVE-2019-20503 in Safari
Summary
by MITRE
usrsctp before 2019-12-20 has out-of-bounds reads in sctp_load_addresses_from_init.
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Analysis
by VulDB Data Team • 05/05/2025
The vulnerability identified as CVE-2019-20503 affects the usrsctp library version prior to the 2019-12-20 release, specifically within the sctp_load_addresses_from_init function. This issue represents a critical security flaw that allows attackers to perform out-of-bounds memory reads, potentially leading to information disclosure, system instability, or further exploitation. The usrsctp library serves as a user-space implementation of the Stream Control Transmission Protocol, widely utilized in applications requiring reliable data transfer over IP networks. The vulnerability manifests when processing SCTP initialization messages containing malformed address information, creating opportunities for attackers to access memory regions beyond the intended buffer boundaries. Such out-of-bounds reads can expose sensitive data from adjacent memory locations, including cryptographic keys, session tokens, or other confidential information stored within the application's memory space.
The technical root cause of this vulnerability lies in insufficient input validation and boundary checking within the sctp_load_addresses_from_init function. When the library processes incoming SCTP INIT messages, it fails to properly validate the length and structure of address parameters contained within these messages. This deficiency allows attackers to craft specially crafted INIT messages that contain malformed address lists, causing the function to read memory locations that extend beyond the allocated buffer boundaries. The vulnerability is classified under CWE-129 as an Improper Validation of Array Index, specifically manifesting as an out-of-bounds read condition. The flaw demonstrates characteristics consistent with memory safety issues commonly found in C/C++ implementations where buffer overflow protections are inadequate or absent. The function's failure to perform proper bounds checking on array indices or memory access operations creates a predictable pattern of memory corruption that can be exploited systematically.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can facilitate more sophisticated attacks within the attacker's threat model. An adversary capable of sending crafted SCTP packets to a vulnerable system can potentially extract sensitive information from memory, leading to credential compromise, session hijacking, or exposure of cryptographic material. The vulnerability affects systems that rely on usrsctp for network communication, particularly those implementing SCTP for signaling protocols, multimedia streaming, or real-time communication applications. The out-of-bounds read condition can cause application crashes or undefined behavior, potentially enabling denial-of-service attacks against services that depend on the affected library. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving information gathering and privilege escalation, as it provides attackers with additional information that could be leveraged for further exploitation. The vulnerability's impact is particularly concerning in environments where SCTP is used for critical communications, such as telecommunications infrastructure, industrial control systems, or financial services applications.
Mitigation strategies for CVE-2019-20503 center on immediate software updates to the usrsctp library version 2019-12-20 or later, which includes proper bounds checking and input validation. Organizations should conduct comprehensive vulnerability assessments to identify all systems utilizing the affected library and prioritize patching efforts accordingly. Network segmentation and monitoring can provide additional layers of defense by detecting anomalous SCTP traffic patterns that may indicate exploitation attempts. Implementing strict input validation at network boundaries and employing intrusion detection systems capable of identifying malformed SCTP packets can help reduce the attack surface. Security teams should also consider deploying application-level firewalls or proxies that can filter and validate SCTP traffic before it reaches vulnerable applications. The fix implemented in the updated library version addresses the core issue by enforcing proper boundary checks on address parameter processing, ensuring that memory accesses remain within valid buffer limits. Additionally, organizations should review their SCTP implementation practices and consider adopting more robust error handling mechanisms that prevent similar vulnerabilities from occurring in other network protocol implementations.