Socket Binding Vulnerability in Linux Kernel
CVE-2025-21756

7.8HIGH

Key Information:

Vendor: Linux
Status: Linux
Vendor: CVE Published:; 27 February 2025

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What is CVE-2025-21756?

CVE-2025-21756 is a critical vulnerability found in the Linux kernel's Virtual Socket (vsock) implementation, which is used for inter-process communication between virtual machines and their host. This vulnerability arises from improper management of socket bindings during transport reassignment, specifically failing to maintain the correct reference count of sockets. As a result, it can lead to a use-after-free condition, where a process attempts to access memory that has already been freed. This flaw potentially allows local attackers to escalate their privileges to root level, gaining complete control of affected systems. The threat is particularly acute in environments that rely on vsock for communication between virtual machines, posing risks for cloud infrastructures and virtualized environments.

Potential impact of CVE-2025-21756

Privilege Escalation: Attackers can exploit this vulnerability to elevate their privileges to root, giving them full control over the system. This level of access can enable them to execute arbitrary code, manipulate sensitive data, or disrupt core functionalities of the host server.
System Compromise: The ability to gain root access means that attackers can potentially take over the entire system, leading to unauthorized data access, theft, or corruption. Such breaches can have significant repercussions for organizations, including financial loss and damage to reputation.
Exploitation Feasibility: Given that this vulnerability can be reliably exploited with local access and low attack complexity, the risk increases, especially in multi-user environments. Even though local access is a prerequisite, the ability to execute tested exploitation methods makes this vulnerability particularly dangerous, particularly in scenarios where untrusted users have account access.

Affected Version(s)

Linux c0cfa2d8a788fcf45df5bf4070ab2474c88d543a

Linux c0cfa2d8a788fcf45df5bf4070ab2474c88d543a < 42b33381e5e1f2b967dc4fb4221ddb9aaf10d197

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2025-21756
Created by hoefler02

News Articles

CybersecurityNews

CVE-2025-21756

Critical Linux Kernel Vulnerability Exposes Systems to Privilege Escalation Attacks

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.