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Opera telnet URI handler file creation/truncation vulnerability


1.  Gentoo Linux Security Advisory

Version Information

Advisory Reference GLSA 200405-19 / opera
Release Date May 25, 2004
Latest Revision December 30, 2007: 03
Impact normal
Exploitable remote
Package Vulnerable versions Unaffected versions Architecture(s)
www-client/opera < 7.50_beta1 >= 7.50_beta1 All supported architectures

Related bugreports: #50857


A vulnerability exists in Opera's telnet URI handler that may allow a remote attacker to overwrite arbitrary files.

2.  Impact Information


Opera is a multi-platform web browser.


The telnet URI handler in Opera does not check for leading '-' characters in the host name. Consequently, a maliciously-crafted telnet:// link may be able to pass options to the telnet program itself. One example would be the following:


If MyFile exists in the user's home directory and the user clicking on the link has write permissions to it, the contents of the file will be overwritten with the output of the telnet trace information. If MyFile does not exist, the file will be created in the user's home directory.


This exploit has two possible impacts. First, it may create new files in the user's home directory. Second, and far more serious, it may overwrite existing files that the user has write permissions to. An attacker with some knowledge of a user's home directory might be able to destroy important files stored within.

3.  Resolution Information


Disable the telnet URI handler from within Opera.


All Opera users are encouraged to upgrade to the latest version of the program:

Code Listing 3.1: Resolution

# emerge sync

# emerge -pv ">=www-client/opera-7.50_beta1"
# emerge ">=www-client/opera-7.50_beta1"

4.  References


Page updated May 25, 2004

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