SB2014100401 - Gentoo update for Bash

Description

This security bulletin contains information about 4 secuirty vulnerabilities.

1) Memory corruption (CVE-ID: CVE-2014-6277)

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The vulnerability exists due to incorrect parsing of environment variables. A remote attacker can trigger memory corruption and execute arbitrary code on the target system as demonstrated by vectors involving the ForceCommand feature in OpenSSH sshd, the mod_cgi and mod_cgid modules in the Apache HTTP Server, scripts executed by unspecified DHCP clients, and other situations in which setting the environment occurs across a privilege boundary from Bash execution. The vulnerability was introduced by incorrect patching of vulnerabilities #1 (CVE-2014-6271) and #2 (CVE-2014-7169).

Successful exploitation results in arbitrary code execution on the vulnerable system.

Note: this vulnerability was being actively exploited in the wild.

2) Memory corruption (CVE-ID: CVE-2014-7186)

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The weakness exists due to out-of-bounds memory access while handling multiple "<<EOF" declarations. A remote attacker can trigger memory corruption and execute arbitrary code.

Exploitation example:

bash -c 'true <<EOF <<EOF <<EOF <<EOF <<EOF <<EOF <<EOF <<EOF <<EOF <<EOF <<EOF <<EOF <<EOF <<EOF' ||  echo "CVE-2014-7186 vulnerable, redir_stack"

Successful exploitation results in arbitrary code execution on the vulnerable system.

Note: this vulnerability was being actively exploited.

3) Off-by-one error (CVE-ID: CVE-2014-7187)

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The weakness exists due to off-by-one-error when handling deeply nested flow control constructs. A remote attacker can trigger memory corruption and execute arbitrary code with privileges of the current user.

Exploitation example:

(for x in {1..200} ; do echo "for x$x in ; do :"; done; for x in {1..200} ; do echo done ; done) | bash ||
echo "CVE-2014-7187 vulnerable, word_lineno"

Successful exploitation results in arbitrary code execution on the vulnerable system.

Note: this vulnerability was being actively exploited.

4) Command injection (CVE-ID: CVE-2014-6278)

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The weakness exists due to an incomplete fix related to the parsing of user scripts. By using attack vectors involving the ForceCommand feature in OpenSSH sshd, the mod_cgi and mod_cgid modules in the Apache HTTP Server, a remote attacker can execute arbitrary code with privileges of the current user. The vulnerability was introduced by incorrect patching of vulnerabilities #1 (CVE-2014-6271),  #2 (CVE-2014-7169) and #3 (CVE-2014-6277)

Successful exploitation results in arbitrary code execution on the vulnerable system.

Note: this vulnerability was being actively exploited.

Remediation

Install update from vendor's website.

References

• https://security.gentoo.org/glsa/201410-01