CVE-2026-104593 in osmo-msc
Summary
by MITRE • 10/26/2026
osmo-msc through 1.15.0 contains a stack-based buffer overflow in decode_mme_name() in src/libmsc/sgs_iface.c. This allows a remote attacker to cause a denial of service.
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Analysis
by VulDB Data Team • 10/26/2026
The vulnerability identified in osmocom MSC versions up to and including 1.15.0 represents a critical security flaw within the GSM Signaling System No. 7 (SS7) interface implementation, specifically located in the decode_mme_name function found in the src/libmsc/sgs_iface.c source file. This component is responsible for processing signaling messages related to the SGS interface, which facilitates communication between the Mobile Switching Center and the Mobility Management Entity in LTE networks. The core technical issue stems from a stack-based buffer overflow condition that occurs when the application processes incoming MME names during message decoding operations. In C programming languages, such as the one used for osmocom MSC development, manual memory management is required, and failure to strictly validate input lengths against allocated buffer sizes creates exploitable conditions. When an attacker sends a specially crafted SGS message containing an MME name field that exceeds the expected or hardcoded limit of the destination buffer on the call stack, the excess data overwrites adjacent memory locations. This overwrite corrupts critical control structures such as return addresses and saved frame pointers, leading to immediate instability in the execution flow of the process.
From a technical perspective, this flaw is classified under CWE-121, which denotes a stack-based buffer overflow. The vulnerability arises because the decode_mme_name function does not adequately check the length of the input string before copying it into a fixed-size local variable on the stack. In network-facing services like MSCs that handle high volumes of signaling traffic from potentially untrusted or compromised upstream nodes in the telecommunications infrastructure, this lack of bounds checking is particularly dangerous. The SGS interface connects to external entities such as Home Location Registers and other core network elements, meaning an attacker with access to the SS7 or Diameter networks can inject malicious payloads directly into the processing pipeline. While stack-based buffer overflows are often associated with arbitrary code execution due to control flow hijacking capabilities, in this specific instance within osmocom MSC 1.15.0 and earlier versions, the primary observed impact is a denial of service. The corruption of the stack leads to segmentation faults or immediate termination of the signaling process, effectively taking down the affected node's ability to handle call setup, location updates, or handovers for connected mobile subscribers.
The operational impact of this vulnerability extends beyond simple application crashes. Since osmocom MSC serves as a central component in managing voice and data sessions for cellular networks, its disruption causes significant service degradation. Subscribers attempting to register with the network may experience failure to attach, leading to loss of connectivity. Existing active calls or data sessions might be abruptly dropped due to the inability of the MSC to process necessary signaling updates or keep-alive messages from other network elements. In a production environment, this can result in widespread service outages affecting hundreds or thousands of users depending on the scale of the deployed instance. Furthermore, if an attacker attempts to exploit the overflow for code execution rather than just causing a crash, they could potentially gain remote control over the server hosting the MSC software. This would allow them to intercept sensitive subscriber data, manipulate routing decisions, or pivot into other parts of the internal network infrastructure, posing severe risks to both privacy and national security in critical telecommunications contexts.
Mitigation strategies for this vulnerability primarily involve upgrading the osmocom MSC software to a version later than 1.15.0 where the decode_mme_name function has been patched with proper input validation mechanisms. Developers should ensure that all string inputs from network interfaces are validated against maximum allowed lengths before being copied into fixed-size buffers. Implementing strict bounds checking and using safer string handling functions can prevent such overflows. Additionally, organizations deploying osmocom MSC in production environments should implement defense-in-depth measures. This includes placing the signaling interface behind firewalls that filter out malformed SS7 or Diameter messages, utilizing intrusion detection systems configured to recognize patterns indicative of buffer overflow attempts, and restricting network access to only trusted peer nodes. Regular security audits and static code analysis tools can also help identify similar vulnerabilities in other parts of the codebase before they are deployed into live networks. Adhering to secure coding standards such as those outlined by CERT C or OWASP guidelines for memory safety is essential to maintaining the integrity of telecommunications infrastructure against evolving cyber threats.