Vulnerability in rpc.statd

Original issue date: April 24, 1996
Last revised: December 5, 1997
Added information for NCR Corporation.

A complete revision history is at the end of this file.

The CERT Coordination Center has received reports of a vulnerability in rpc.statd (rpc.statd is also known as statd on some systems). We have received reports of this vulnerability being exploited.

If exploited, this vulnerability can be used to remove any file that the root user can remove or to create any file that the root user can create.

Section III and Appendix A contain information from vendors. Appendix B contains an example of a possible workaround.

We will update this advisory as we receive additional information. Please check advisory files regularly for updates that relate to your site.

I. Description

rpc.statd, also called statd, is the NFS file-locking status monitor. It interacts with rpc.lockd, also called lockd, to provide the crash and recovery functions for file locking across NFS.

Note that rpc.lockd and rpc.statd work together; if either is running, both must run.

rpc.lockd and rpc.statd can be safely turned off on a machine if that machine is neither an NFS client nor an NFS server. Consult your system documentation to learn how to turn these services off and not restart them when a system is rebooted.

If a machine where rpc.lockd and rpc.statd have been disabled becomes either an NFS server or an NFS client, then both rpc.lockd and rpc.statd should be turned back on.

NFS is stateless, which means that NFS clients and servers can be rebooted without a loss of file integrity due to NFS. In contrast, NFS file locking is stateful. To achieve this stateful nature in a stateless environment, rpc.lockd must work with rpc.statd to add state to file locking.

To understand what rpc.statd does, it is first necessary to understand what rpc.lockd does. rpc.lockd processes lock requests that are sent either locally by the kernel or remotely by another lock daemon. rpc.lockd forwards lock requests for remote NFS files to the NFS server's lock daemon using Remote Procedure Calls (RPC).

rpc.lockd then requests monitoring service from the status monitor daemon, rpc.statd, running on the NFS server. Monitoring services are needed because file locks are maintained in the NFS server kernel. In the event of a system crash or reboot, all NFS locks would normally be lost. It is rpc.statd that adds stateful file locking.

When an NFS server reboots, rpc.statd causes the previously held locks to be recovered by notifying the NFS client lock daemons to resubmit previously granted lock requests. If a lock daemon fails to secure a previously granted lock on the NFS server, it sends SIGLOST to the process that originally requested the file lock.

The vulnerability in rpc.statd is its lack of validation of the information it receives from what is presumed to be the remote rpc.lockd. Because rpc.statd normally runs as root and because it does not validate this information, rpc.statd can be made to remove or create any file that the root user can remove or create on the NFS server.

II. Impact

Any file that root could remove can be removed by rpc.statd. Any file that root could create can be created by rpc.statd, albeit with mode 200.

III. Solution

The general solution to this problem is to replace the rpc.statd daemon with one that validates the information sent to it by the remote rpc.lockd. We recommend that you install a patch from your vendor if possible. If a patch is not available for your system, we recommend contacting your vendor and requesting that a patch be developed as soon as possible. In the meantime, consider whether the information in Appendix B is applicable to your site.

Vendor Information

Below is a list of vendors who have provided information. Details are in Appendix A of this advisory. We will update the advisory as we receive more information.

Berkeley Software Design, Inc.
Cray Research, Inc.
Data General Corporation
Harris Computer Systems Corp.
Hewlett-Packard Company
IBM Corporation
NCR Corporation
NEC Corporation
NeXT Software, Inc.
The Santa Cruz Operation
Silicon Graphics. Inc.
Sony Corporation
Sun Microsystems, Inc.
TGV/Cisco Systems, Inc.

If your vendor's name is not on this list, please contact the vendor directly.

Appendix A: Vendor Information

Below is information we have received from vendors concerning the vulnerability described in this advisory. If you do not see your vendor's name, please contact the vendor directly for information.

Apple Computer, Inc.


An upgrade to A/UX version 3.1 (and 3.1.1) for this vulnerability is available. The upgrade replaces the rpc.statd binary with a new, improved version. It is available via anonymous FTP from


Uncompress(1) this file and replace the existing version in /etc. Modify the entry for rpc.statd in /etc/inittab to "respawn" instead of "wait".
Kill the running rpc.statd and restart.

Earlier versions of A/UX are not supported by this patch. Users of previous versions are encouraged to update their system or disable rpc.statd.

AIX for the Apple Network Server

An upgrade to AIX version 4.1.4 for the Network Server which resolves this vulnerability is available. The PTF replaces the rpc.statd binary and related programs with new, improved versions.

To determine if you already have APAR IX55931 on your system, run the following command:

instfix -ik IX55931

Or run the following command:

lslpp -h

Your version of should be or later.

The PTF for this APAR is available via anonymous FTP from


Place this file in /usr/sys/inst.images or another directory of your choice. To install the PTF, start smit using the following fast path:

# smit install_selectable

Select the menu item "Install Fileset Updates by Fix" and provide the name of the directory in which the PTF was placed. Enter OK and in the next dialog, enter the APAR number, IX55931, in the "FIXES" item. For information about the other options in this dialog, see the manual page for installp(1). Enter OK, exit smit and restart the system.

Customers should contact their reseller for any additional information.

Berkeley Software Design, Inc.

BSD/OS is not vulnerable.

Cray Research, Inc.

This problem has been tracked with SPR 99983 and reported
with Field notice 2107. Since statd is only available on 9.0 systems fixes have been provided for UNICOS 9.0 and higher.

Data General Corporation

Data General has fixed this vulnerability in DG/UX R4.11 Maintenance Update 2 (R4.11MU02).

Digital Equipment Corporation

For updated information, please refer to the Digital Equipment Corporation Vendor Bulletin #96.0383, available in

Note: Non-contract/non-warranty customers should contact local Digital support channels for information regarding these kits.

As always, Digital urges you to periodically review your system management and security procedures. Digital will continue to review and enhance the security features of its products and work with customers to maintain and improve the security and integrity of their systems.

Harris Computer Systems Corporation

All versions of NightHawk CX/SX and CyberGuard CX/SX are not vulnerable.

All versions of NightHawk CX/UX and PowerUX are vulnerable.
Users are advised, until patches are available, to use the workaround in the advisory.

Hewlett-Packard Company

The rpc.statd daemon that ships with HP systems contains a vulnerability that could allow a remote user to delete files on the system running rpc.statd.

Hewlett Packard is delivering a set of operating system dependent patches which contain a new version of rpc.statd. Accompanying each patch is a README file which discusses the general purpose of the patch and describes how to apply it to your system.

Recommended solution:

Apply one of the following patches based on your system hardware and operating system revision:

s300/s400 9.X - PHNE_7372 (rpc.statd)
s700/s800 9.X - PHNE_7072 (NFS Megapatch)
s700/s800 10.X - PHNE_7073 (NFS Megapatch)

The patches described above provide a new version of the rpc.statd executable which fixes the vulnerability.

To subscribe to automatically receive future NEW HP Security Bulletins please refer to information in

IBM Corporation

See the appropriate release below to determine your action.

AIX 3.2

Apply the following fix to your system:

APAR - IX56056 (PTF - U441411)

To determine if you have this PTF on your system, run the following command:

lslpp -lB U441411

AIX 4.1

Apply the following fix to your system:

APAR - IX55931

To determine if you have this APAR on your system, run the following command:

instfix -ik IX55931

Or run the following command:

lslpp -h


To Order

APARs may be ordered using FixDist or from the IBM Support Center. For more information on FixDist, reference URL:

or send e-mail to with a subject of "FixDist".

NCR Corporation

The statd binary that shipped with some older NCR MP-RAS SVR4 releases contains a vulnerability that could allow a remote user to create or delete files on a server running statd.

NCR is delivering a set of operating system dependent patches which contain a new version of statd. Accompanying each patch is a README file which discusses the general purpose of the patch and describes how to apply it to your system.

Recommended solution:

Apply one of the following patches based on your operating system revision:

MP-RAS 2.03.x - PNFS203 (Version after 7/26-96)
MP-RAS 3.00.x - PNFS300 (Version after 8/19-96)
MP-RAS 3.01.x and later - Not vulnerable

The patches described above provide a new version of the statd executable, which fixes the vulnerability.

NEC Corporation

Some systems are vulnerable and patches are available through anonymous FTP from
UP-UX/V (Rel4.2MP) R5.x NECu5s003.COM.pkg
Results of sum = 3060 266
md5 = 79E626B99A55FB0DBCE6EE642874570A
R6.x NECu6s003.COM.pkg
Results of sum = 47304 272
md5 = 9FC9E993A5AB51291BF4817D3D70FBFD
R7.x NECu7s003.COM.pkg
Results of sum = 46470 291
md5 = 59CA6887078AF88EA165AFD3BF5A1374
EWS-UX/V (Rel4.2) R7.X NECe7s004.COM.pkg
Results of sum = 3827 194
md5 = 4D40D9258DAB7EA41C30789609818330
R8.x NECe8s004.COM.pkg
Results of sum = 24399 199
md5 = 40B4CB1140791C14D1B604B6E8CB5FCB
(except EWS4800/110N)
Results of sum = 23250 203
md5 = 5AD8BED137AAE7D0067EF3120574786C
Results of sum = 3972 201
md5 = 28B2FA99F5200F81C5465571EF27E08B
R10.x NECeas004.COM.pkg
Results of sum = 51969 205
md5 = B6E12017E66DC8DC38FBE78CA1F0B0F0
EWS-UX/V (Rel4.2MP) R10.x NECmas007.COM.pkg
Results of sum = 48060 291
md5 = 42F8AE832071F033E21D8718A3670D76
UX/480O R11.x NECmbs010.COM.pkg
Results of sum = 24885 335
md5 = 7A14CBE4EA9B2470E340B5EEFD523F95

For further information contact: . We encourage you contact the vendor directly if you have any questions.

NeXT Software, Inc.

This vulnerability will be fixed in release 4.0 of OpenStep for Mach, scheduled for 2Q96.

The Santa Cruz Operation, Inc.

These are not vulnerable:

SCO UnixWare 2.x.
SCO OpenServer 3.0, 5
SCO Open Desktop 2.x, 3.x
SCO NFS 1.x.x.

Silicon Graphics, Inc.

All versions of IRIX earlier than 6.2 are vulnerable.

IRIX 6.2 is not vulnerable.

The the most current information appears in

Sony Corporation

        NEWS-OS 4.2.1   vulnerable; Patch 0124 [rpc.statd] is available.
        NEWS-OS 6.0.3   vulnerable; Patch SONYP6063 [lockd/statd 2] is
        NEWS-OS 6.1     vulnerable; Patch SONYP6176 [lockd/statd] is
        NEWS-OS 6.1.1   vulnerable; Patch SONYP6207 [lockd/statd] is
        Patches are available via anonymous FTP in the
        /pub/patch/news-os/un-official directory on []:
        4.2.1a+/0124.doc       describes about patch 0124 [rpc.statd]
        4.2.1a+/0124_C.pch     patch for NEWS-OS 4.2.1C/a+C
        4.2.1a+/0124_R.pch     patch for NEWS-OS 4.2.1R/RN/RD/aRD/aRS/a+R
        6.0.3/SONYP6063.doc    describes about patch SONYP6063 [lockd/statd 2]
        6.0.3/SONYP6063.pch    patch for NEWS-OS 6.0.3
        6.1/SONYP6176.doc      describes about patch SONYP6176 [lockd/statd]
        6.1/SONYP6176.pch      patch for NEWS-OS 6.1
        6.1.1/SONYP6207.doc    describes about patch SONYP6207 [lockd/statd]
        6.1.1/SONYP6207.pch    patch for NEWS-OS 6.1.1

If you need further information, contact your dealer.

Sun Microsystems, Inc.

The following patches are now available to fix the vulnerabilities in rpc.statd. More details are in Sun Microsystems Security Bulletin #00135, dated May 21, 1996.

A. Solaris 2.x (SunOS 5.x) patches

Patches which replace the affected statd executable are available for every supported version of SunOS 5.x.
OS version Patch ID

SunOS 5.3 102932-02
SunOS 5.4 102769-03
Sun0S 5.4_X86 102770-03
SunOS 5.5 103468-01
SunOS 5.5_X86 103469-01

B. Solaris 1.x (SunOS 4.1.x) patches

For SunOS 4.1.x, the fix is supplied in a new version of the "UFS file system and NFS locking" jumbo patch.
OS version Patch ID

SunOS 4.1.3 100988-05
SunOS 4.1.3_U1 101592-07
SunOS 4.1.4 102516-04

In the checksum table we show the BSD and SVR4 checksums and MD5 digital signatures for the compressed tar archives.

In the checksum table we show the BSD and SVR4 checksums and MD5 digital signatures for the compressed tar archives.

File             BSD          SVR4        MD5
Name            Checksum    Checksum    Digital Signature ---------------  -----------  ---------  -------------------------------- 100988-05.tar.Z  10148 444    4116 888    ACE925E808A582D6CF9209FE7A51D23B 101592-07.tar.Z  21219 346    32757 692  7B7EE4BD5B2692249FDB9178746AA71B 102516-04.tar.Z  65418 201    61604 401  DB87F3DDA2F12FE2CFBB8B56874A1756 102769-03.tar.Z  38936 74    64202 148  9A8E4D9BE8C58FD532EE0E2140EF7F85 102770-03.tar.Z  04518 71    23051 141  F646E2B7AD66EEFBB32F6AB630796AF8 102932-02.tar.Z  34664 70    45816 139  66CB7F6AE48784A884BA658186268C41 103468-01.tar.Z  30917 82    46790 164  84680D9A0D2AEF62FFE1382C82684BE5 103469-01.tar.Z  31245 82    52288 164  F22AEB0FD91687DAB8ADC4DF10348DE8

The checksums shown above are from the BSD-based checksum (on 4.1.x, /bin/sum; on SunOS 5.x, /usr/ucb/sum) and from the SVR4 version on on SunOS 5.x (/usr/bin/sum).

Customers with Sun support contracts can obtain patches from:

- SunSolve Online
- Local Sun answer centers, worldwide
- SunSITEs worldwide

The patches are available via World Wide Web at

Customers without support contracts may now obtain security patches, "recommended" patches, and patch lists via SunSolve Online.

TGV/Cisco Systems, Inc.

Cisco MultiNet for OpenVMS is not vulnerable.

Appendix B: Example Workaround Scenario

The information given below was provided to the CERT/CC by Wolfgang Ley of DFN-CERT. It is reproduced here as an example of how to run the statd daemon as a user other than root on a Solaris system. This workaround may not be directly applicable on other vendor's systems, but an analogous solution may be possible. Please contact your vendor for assistance.

The statd daemon under Solaris 2.4 and 2.5 starts without problems if the following steps are taken.

1) Go into single user mode (ensure rpcbind and statd are not running)
2) Create a new user, e.g., "statd" with a separate uid/gid
3) Chown statd /var/statmon/* /var/statmon/*/*
4) Chgrp statd /var/statmon/* /var/statmon/*/*
5) Edit /etc/init.d/nfs.client startup script and change the start of the statd from:

               /usr/lib/nfs/statd > /dev/console 2>&1
               /usr/bin/su - statd -c "/usr/lib/nfs/statd" > /dev/console 2>&1
6) Reboot the system

The CERT Coordination Center thanks Andrew Gross of the San Diego Supercomputer Center for reporting this problem and Wolfgang Ley of DFN-CERT for his support in responding to this problem.

Copyright 1996 Carnegie Mellon University.

Revision History
Dec. 5, 1997  Appendix A - Added for NCR Corporation.
Sep. 24, 1997 Updated copyright statement
Nov. 12, 1996 Appendix A, SGI - replaced a URL with a pointer to updated
Sep. 18, 1996 Revised opening paragraph.
Aug. 30, 1996 Information previously in the README was inserted into the
              Appendix A, IBM - put a new URL in the "To Order" section.
              Appendix A, Sun - removed a workaround for SunOS 4.x (patches now
Aug. 01, 1996 Appendix A, Hewlett-Packard - updated information.
July 26, 1996 Appendix A, NEC - added patch information.
July 5, 1996  Appendix A, Digital - added pointer to updated vendor
July 1, 1996  Appendix A, SGI - added pointer to release notes.
May 23, 1996  Appendix A, Sun - added pointer to patches.
May 10, 1996  Sec. I - added clarification about disabling rpc.lockd and
              Appendix A, TGV/Cisco Systems - added an entry.
              Appendix A, Sun - added a workaround.