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sharutils: Insecure temporary file creation


1.  Gentoo Linux Security Advisory

Version Information

Advisory Reference GLSA 200504-06 / sharutils
Release Date April 06, 2005
Latest Revision April 06, 2005: 01
Impact normal
Exploitable local
Package Vulnerable versions Unaffected versions Architecture(s)
app-arch/sharutils < 4.2.1-r11 >= 4.2.1-r11 All supported architectures

Related bugreports: #87939


The unshar utility is vulnerable to symlink attacks, potentially allowing a local user to overwrite arbitrary files.

2.  Impact Information


sharutils is a collection of tools to deal with shar archives.


Joey Hess has discovered that the program unshar, which is a part of sharutils, creates temporary files in a world-writable directory with predictable names.


A local attacker could create symbolic links in the temporary files directory, pointing to a valid file somewhere on the filesystem. When unshar is executed, this would result in the file being overwritten with the rights of the user running the utility, which could be the root user.

3.  Resolution Information


There is no known workaround at this time.


All sharutils users should upgrade to the latest version:

Code Listing 3.1: Resolution

# emerge --sync
# emerge --ask --oneshot --verbose ">=app-arch/sharutils-4.2.1-r11"

4.  References


Page updated April 06, 2005

Summary: This is a Gentoo Linux Security Advisory

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