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posted by n1 on Thursday September 25 2014, @01:59AM   Printer-friendly
from the well,-that's-not-ideal dept.

Ars reports that a new bug has been found in GNU Bash allows remote attackers to execute arbitrary code by setting the process trailing strings after function definitions in the values of environment variables.

This bug is reported to be present in RHEL (ver 4 through 7), Fedora, CentOS (ver 5 through 7), Ubuntu (ver 10.04 LTS, 12.04 LTS, and 14.04 LTS), Debian, and even OS X Mavericks.

This bug is exploitable through Apache servers with mod_cgi and mod_cgid loaded, OpenSSH, malicious DHCP servers in a compromised wireless access point through dhclient, as well as the CUPS printing system.

The Ars also includes a simple single liner that will test your setup for the newly found discovery:

env x='() { :;}; echo vulnerable' bash -c "echo this is a test"

A vulnerable system will output the following:

vulnerable
 this is a test

While a patched or unaffected system outputs:

bash: warning: x: ignoring function definition attempt
bash: error importing function definition for `x'
this is a test

A patch is already out, so administrators are advised to update Bash.

Editor's Update: Security Engineer Tavis Ormandy has said "The bash patch seems incomplete to me, function parsing is still brittle".

$ env X='() { (a)=>\' sh -c "echo date"; cat echo

 
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  • (Score: 2) by fnj on Friday September 26 2014, @09:18AM

    by fnj (1654) on Friday September 26 2014, @09:18AM (#98519)

    It doesn't matter whether you believe it or not. It's true.

    Now, as to BSD systems where you install bash. It still doesn't make /bin/sh a symlink to bash, like most linux distros do - a sloppy, brain dead practice. So as far as I know, even if bash is installed, BSD is not sysceptible to the exploit as it is explained.

    P.S., debian doesn't have /bin/sh symlinked to bash either. It symlinks it to dash. I don't believe dash has the bug. At least it passes the test scripts I've tried. You have to modify the stupid test scripts to run /bin/sh, not bash. After all, that's what system() runs: /bin/sh, not bash. So as far as I can tell, debian is OK, too.

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