CVE-2026-104598 in libosmo-sigtran
Summary
by MITRE • 10/26/2026
libosmo-sigtran through 2.2.1 contains an out-of-bounds read in the M3UA NOTIFY decoder in src/m3ua.c. This allows a remote attacker to obtain sensitive information.
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Analysis
by VulDB Data Team • 10/26/2026
The vulnerability identified within libosmo-sigtran versions up to and including 2.2.1 represents a critical security flaw located specifically in the Message Transfer Part Level Three User Adaptation layer, or M3UA NOTIFY decoder. This component is responsible for processing signaling messages that facilitate communication between Signaling System No. 7 networks and IP-based transport networks. The core technical issue stems from an out-of-bounds read operation within the source file src/m3ua.c. When the application parses incoming NOTIFY messages, it fails to adequately validate the length or bounds of specific data fields before attempting to access memory locations associated with those fields. This lack of rigorous boundary checking allows the parser to read beyond the allocated buffer limits defined by the message structure.
From a technical perspective, this flaw is classified under Common Weakness Enumeration as CWE-125, which denotes an out-of-bounds read vulnerability. The mechanism involves the decoder reading memory addresses that are not part of the intended data payload but reside in adjacent memory regions. In C-based applications like libosmo-sigtran, such errors do not typically result in immediate application crashes if only a single byte or small block is accessed incorrectly, which makes them particularly insidious and difficult to detect through standard testing methods unless specific fuzzing techniques are employed. The attacker can craft maliciously formatted M3UA NOTIFY messages that trigger this erroneous memory access pattern during the decoding process on the server side.
The operational impact of this vulnerability centers on information disclosure rather than code execution or denial of service, although the latter remains a potential secondary consequence depending on what sensitive data resides in the adjacent memory space. By exploiting this out-of-bounds read, a remote attacker can extract arbitrary contents from the application's memory heap or stack. This may include private keys, session tokens, authentication credentials, or other proprietary signaling data that was previously loaded into memory for processing previous messages. The ability to leak such sensitive information compromises the confidentiality of the telecommunications infrastructure and potentially facilitates further attacks against the network by providing attackers with valuable intelligence about internal configurations or user sessions.
In terms of threat modeling, this vulnerability aligns with MITRE ATT&CK technique T1005, which refers to Data from Local System Retrieval. The attacker leverages a remote input vector to exfiltrate data that is not directly exposed through normal application interfaces but becomes accessible due to the memory corruption flaw. This type of attack requires no user interaction and can be executed remotely if the M3UA service port is exposed to untrusted networks, highlighting the importance of strict network segmentation for signaling gateways.
Mitigation strategies must focus on both immediate patching and long-term architectural improvements. The primary remediation step is to upgrade libosmo-sigtran to a version later than 2.2.1 where this specific bounds-checking logic has been corrected in src/m3ua.c. Developers should ensure that all incoming message lengths are strictly validated against buffer sizes before any memory access occurs. Additionally, implementing Address Sanitizer tools during the development and testing phases can help detect such out-of-bounds accesses early in the software lifecycle. For deployed systems where immediate patching is not feasible, network-level controls such as deep packet inspection firewalls should be configured to inspect M3UA traffic for malformed message structures that exceed expected length parameters, thereby blocking malicious payloads before they reach the vulnerable decoder logic.