Integer Overflow Vulnerability in libssh2 Publickey Subsystem

CVE-2026-58050

What is CVE-2026-58050?

CVE-2026-58050 is an integer overflow vulnerability found in the libssh2 library, which is widely used for implementing SSH2 protocols in applications for secure communication over networks. This vulnerability arises from the way libssh2 handles data from a publickey-subsystem response. Specifically, the library reads a 32-bit attribute count provided by an attacker-controlled SSH server and subsequently uses that value in a memory allocation calculation without proper bounds checking. On 32-bit systems, this can lead to integer overflow, resulting in a heap buffer overflow when the library attempts to allocate memory for the attribute data.

The implications of such a vulnerability are severe, as it can allow an attacker to manipulate the memory allocated for the SSH connection, potentially leading to unauthorized data access or execution of arbitrary code on the client-side. This makes systems utilizing libssh2 susceptible to various attacks, including remote code execution if exploited successfully.

Potential impact of CVE-2026-58050

1. Heap Buffer Overflow: The vulnerability creates a pathway for heap buffer overflow conditions, which can be exploited by attackers to overwrite critical memory locations. This can lead to system crashes, instability, or the execution of arbitrary code, potentially compromising the security of the affected system.

2. Unauthorized Data Access: An attacker can exploit this vulnerability to gain unauthorized access to sensitive information or manipulate the data being processed by the libssh2 client. This could facilitate data breaches or leakage of confidential data, particularly in environments where sensitive transactions or communications are conducted.

3. Increased Risk from Malicious Servers: Since the vulnerability requires interaction with a malicious SSH server, it elevates the risk for users who might connect to untrusted or compromised servers. Attackers operating such servers can leverage the vulnerability to control or exploit connecting clients, increasing the overall threat landscape for users of libssh2.

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