CVE-2024-36964 in Linux
Summary
by MITRE • 06/03/2024
In the Linux kernel, the following vulnerability has been resolved:
fs/9p: only translate RWX permissions for plain 9P2000
Garbage in plain 9P2000's perm bits is allowed through, which causes it to be able to set (among others) the suid bit. This was presumably not the intent since the unix extended bits are handled explicitly and conditionally on .u.
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Analysis
by VulDB Data Team • 12/17/2025
The vulnerability CVE-2024-36964 affects the Linux kernel's 9P file system implementation, specifically targeting the 9P2000 protocol version. This issue resides within the file system layer at fs/9p where permission handling logic fails to properly validate permission bits for plain 9P2000 connections. The flaw allows malicious actors to manipulate permission bits in ways that were not intended by the protocol design, creating potential security risks through improper access control mechanisms.
The technical root cause stems from insufficient validation of permission bits in the 9P2000 protocol implementation. When processing file permissions, the system accepts garbage values in plain 9P2000's permission bits without proper sanitization, which enables attackers to set privileged bits such as the suid bit. This occurs because the code does not properly filter or translate permission bits for plain 9P2000 connections, unlike the more secure handling of unix extended bits that are explicitly checked and conditionally processed through the .u. mechanism. The vulnerability represents a classic case of inadequate input validation where malformed permission data can be interpreted as legitimate privileged operations.
The operational impact of this vulnerability extends beyond simple permission mismanagement to potentially enable privilege escalation attacks. When the suid bit can be set through malformed permission bits, it creates opportunities for attackers to gain elevated privileges on systems running affected kernel versions. This is particularly concerning in environments where 9P file systems are used for network file sharing or distributed computing scenarios. The vulnerability affects systems that rely on 9P2000 protocol implementations for file access control, potentially compromising the integrity of file access mechanisms and enabling unauthorized code execution with elevated privileges.
The fix implemented addresses this by ensuring that only appropriate RWX permissions are translated for plain 9P2000 connections, preventing the propagation of garbage permission bits that could enable privilege escalation. This aligns with security best practices for input validation and access control as outlined in the CWE-250 standard for "Execution with Unnecessary Privileges" and follows the principle of least privilege enforcement. Organizations should prioritize patching this vulnerability to prevent potential exploitation, especially in environments where 9P file systems are actively used. The remediation approach follows ATT&CK technique T1068 by addressing privilege escalation vectors through proper permission handling, ensuring that file system access controls maintain their intended security boundaries.