A significant vulnerability in the Linux kernel’s Virtual Socket (vsock) implementation, designated as CVE-2025-21756, has been identified that could allow local attackers to escalate privileges to root level. Cyber Security News is a Dedicated News Platform For Cyber News, Cyber Attack News, Hacking News & Vulnerability Analysis. Security researchers have confirmed that this flaw, which received a CVSS v3.1 Base Score of 7.8 (HIGH), can be reliably exploited on affected systems. For systems that cannot be immediately patched, limiting access to local users and monitoring for suspicious activities related to the vsock subsystem is recommended. CVE-2025-21756 represents a significant security risk for Linux systems. According to the Hoefler report, the vulnerability stems from improper handling of socket bindings during transport reassignment in the vsock subsystem. By using vsock_diag_dump() as a side channel, attackers can leak the memory address of init_net, effectively defeating Kernel Address Space Layout Randomization (KASLR). If exploited, attackers can gain root privileges, potentially leading to complete system compromise, data theft, or service disruption. This can create a scenario where subsequent calls to vsock_bind() assume the socket is in the unbound list and call __vsock_remove_bound(), leading to the use-after-free condition. This vulnerability affects all Linux distributions running vulnerable kernel versions. The issue is particularly concerning for cloud environments and virtualized systems that rely heavily on the vsock functionality for guest-host communications. Gurubaran is a co-founder of Cyber Security News and GBHackers On Security. Specifically, the issue occurs in a sequence where the socket’s reference counter is incorrectly decremented, leading to a use-after-free condition.
This Cyber News was published on cybersecuritynews.com. Publication date: Tue, 29 Apr 2025 08:00:07 +0000