NFS server could allow remote users to create device files through mknod
| nfs-mknod (78) |  High Risk |
Description:
A potentially vulnerable version of NFS MKNOD has been detected as running. Found on some older NFS servers, NFS MKNOD may allow normal users to create special devices that could require root access. When non-administrative users can do this, then an attacker could create a kmem (kernel memory) device and change access to root and circumvent system security.
This attack allows an attacker to map a remote volume to any resource on the target system, including hard drives, microphones, video cameras, and monitors. With this level of access, an attacker effectively controls the system.
Consequences:
Gain Privileges
Remedy:
Upgrade to the latest version of the NFS server, available from your vendor. Many mountd programs support a -nodev option that turns off the ability to create a device. Contact your vendor or refer to your operating system documentation for more information.
For Sun systems:
Apply the NFS jumbo patch (Patch-ID# 100173-13), available from the Sun Microsystems Web site. See References.
References:
- CERT Advisory CA-1991-21: SunOS NFS Jumbo and fsirand Patches.
- CERT Advisory CA-1992-15: Multiple SunOS Vulnerabilities Patched.
- CERT Advisory CA-1993-15: /usr/lib/sendmail, /bin/tar, and /dev/audio Vulnerabilities.
- CERT Advisory CA-1994-02: Revised Patch for SunOS /usr/etc/rpc.mountd Vulnerability.
- CERT Advisory CA-1994-15: NFS Vulnerabilities.
- CVE-1999-0084: Certain NFS servers allow users to use mknod to gain privileges by creating a writable kmem device and setting the UID to 0.
Platforms Affected:
- Compaq Tru64
- Data General DG/UX
- IBM AIX
- IETF NFS
- Linux Kernel
- SCO SCO Unix
- SGI IRIX
- Sun Solaris
- Various vendors Unix running NFS
- WindRiver BSDOS
- HP-UX
Reported:
May 01, 1990
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