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.
Platforms Affected:
- Compaq, Tru64
- Data General, DG/UX
- HP, HP-UX
- IBM, AIX
- Linux, Kernel
- SCO, SCO Unix
- SGI, IRIX
- Sun, Solaris
- Various vendors, NFS
- Various vendors, Unix running NFS
- WindRiver, BSDOS
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.
Consequences:
Gain Privileges
References:
- CERT Advisory CA-1991-21, SunOS NFS Jumbo and fsirand Patches at http://www.cert.org/advisories/CA-1991-21.html.
- CERT Advisory CA-1992-15, Multiple SunOS Vulnerabilities Patched at http://www.cert.org/advisories/CA-1992-15.html.
- CERT Advisory CA-1993-15, /usr/lib/sendmail, /bin/tar, and /dev/audio Vulnerabilities at http://www.cert.org/advisories/CA-1993-15.html.
- CERT Advisory CA-1994-02, Revised Patch for SunOS /usr/etc/rpc.mountd Vulnerability at http://www.cert.org/advisories/CA-1994-02.html.
- CERT Advisory CA-1994-15, NFS Vulnerabilities at http://www.cert.org/advisories/CA-1994-15.html.
- 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.
Reported:
May 01, 1990
The information within this database may change without notice. Use of this information constitutes acceptance for use in an AS IS condition. There are NO warranties, implied or otherwise, with regard to this information or its use. Any use of this information is at the user's risk. In no event shall the author/distributor (Internet Security Systems X-Force) be held liable for any damages whatsoever arising out of or in connection with the use or spread of this information.
Copyright (c) 1994-2008 Internet Security Systems, Inc. All rights reserved worldwide.
For corrections or additions please email xforce@iss.net