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Sun Solaris gzip may change permissions of hard linked files

Vulnerability Note VU#635998

Original Release Date: 2004-10-12 | Last Revised: 2004-10-18


Sun Solaris gzip contains a vulnerability that may change the permissions of hard linked files. The specific impact may allow hard linked files compressed by gzip to become readable and able to be modified by unprivileged users.


Gzip is a utility used for compressing and decompressing files. The "-f" (-force) flag is used to force compression or decompression even if the file has multiple hard links. When gzip is used with the "-f" flag on a Sun Solaris 8 machine, it may change the permissions of a hard linked file to 0777, causing a hard link to become readable and able to be modified by unprivileged users, regardless of its previous permission settings.

Note that Solaris 7 and Solaris 9 are not affected by this issue. This vulnerability is only present in versions of gzip prior to 1.3.

The following describes the symptoms of the vulnerability (example provided by the SunSolve Alert) :

    $ ln original-file hardlink
ls -l original-file hardlink
   -rw-r--r--   2 user  staff        293 Jun 24 18:33 hardlink
   -rw-r--r--   2 user  staff        293 Jun 24 18:33 original-file
gzip -f original-file
ls -l original-file* hardlink
   -rwxrwxrwx   1 user  staff        293 Jun 24 18:33 hardlink
   -rw-r--r--   1 user  staff        195 Jun 24 18:33 original-file.gz


Local unprivileged users may be able to read or modify files owned by the user who has invoked gzip as described. Access to system files may inadvertently be granted if the gzip command is issued by a local privileged user.


Apply a patch

SPARC platform: Install Solaris 8 patch 112668-02 or later.
x86 platform: Install Solaris 8 patch 112669-02 or later.

Do not use the force option for gzip

Per Sun Alert ID 57600, avoid using the "-f" or "-force" option with the vulnerable gzip command to work around the problem.

Vendor Information


Sun Microsystems Inc. Affected

Updated:  October 12, 2004



Vendor Statement

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.


We have no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

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This document was written by Will Dormann and is based on the information presented in the Sun Alert notification.

Other Information

CVE IDs: None
Severity Metric: 3.88
Date Public: 2004-10-01
Date First Published: 2004-10-12
Date Last Updated: 2004-10-18 16:44 UTC
Document Revision: 10

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