Linux 'Ghost' vulnerability uncovered

Security researchers at Qualys have discovered a Linux vulnerability, naming it 'Ghost'.

The vulnerability affects the GNU C Library (previously known as glibc) in Linux systems, triggered by calling the gethostbyname*() functions in glibc, used to resolve domain names into IP addresses.

In real terms, this means attackers can take control of a system without knowing any login data.

Wolfgang Kandek, CTO at Qualys, said in a blog post: "There is a remote code execution risk due to this vulnerability. An attacker who exploits this issue can gain complete control of the compromised system."

"During our testing, we developed a proof-of-concept in which we send a specially created e-mail to a mail server and can get a remote shell to the Linux machine. This bypasses all existing protections (like ASLR, PIE and NX) on both 32-bit and 64-bit systems."

However, the impact the vulnerability can have is lower than others that have been discovered over the last 12 months.

Pawan Kinger, director of Deep Security Labs at Trend Micro, commented: "Taken together, the risk of actual exploits targeting GHOST is relatively small compared to other vulnerabilities like Shellshock or Heartbleed. Yes, the underlying vulnerability is problematic, but defense in depth by other vendors means that the actual risk is relatively low."

The reason for this is that the vulnerability has already been patched for newer versions of Linux and Qualys will not reveal the exploit until it has reached its half-life.

Kinger went on to explain that exploitation is also difficult because the attacker will only have four or eight bytes to use in the attack and additional code must be written to an address that the attacker can modify.

"Thirdly, the functions that are the subject of this vulnerability are obsolete. They cannot be used to translate domain names to IPv6 addresses; newer applications use the getaddrinfo() function, which does have IPv6 support," he explained.