Archive for the ‘linux security’ Category

Libssh Releases Update to Patch 9 New Security Vulnerabilities

March 19th, 2019
Libssh2, a popular open source client-side C library implementing the SSHv2 protocol, has released the latest version of its software to patch a total of nine security vulnerabilities. The Libssh2 library is available for all major distributors of the Linux operating systems, including Ubuntu, Red Hat, Debian, and also comes bundled within some distributions and software as a default library

Posted in hacking linux, hacking news, libssh, libssh2, linux security, memory corruption vulnerability, secure shell, server security, ssh exploit, ssh hacking, Vulnerability | Comments (0)

LibSSH Flaw Allows Hackers to Take Over Servers Without Password

October 17th, 2018
A four-year-old severe vulnerability has been discovered in the Secure Shell (SSH) implementation library known as Libssh that could allow anyone to completely bypass authentication and gain unfettered administrative control over a vulnerable server without requiring a password. The security vulnerability, tracked as CVE-2018-10933, is an authentication-bypass issue that was introduced in

Posted in hacking Linux servers, hacking news, libssh, linux security, OpenSSH, secure shell, ssh exploit, ssh hacking, ssh security, Vulnerability | Comments (0)

7-Year-Old Samba Flaw Lets Hackers Access Thousands of Linux PCs Remotely

May 25th, 2017

A 7-year-old critical remote code execution vulnerability has been discovered in Samba networking software that could allow a remote attacker to take control of an affected Linux and Unix machines.

Samba is open-source software (re-implementation of SMB networking protocol) that runs on the majority of operating systems available today, including Windows, Linux, UNIX, IBM System 390, and

Posted in exploit code, hacking Linux servers, hacking news, how to hack linux, linux security, Metasploit Framework, remote code execution, Samba server, Samba Service, Samba vulnerability, smb vulnerability | Comments (0)

5-Year-Old Linux Kernel Local Privilege Escalation Flaw Discovered

December 7th, 2016

A 5-year-old serious privilege-escalation vulnerability has been discovered in Linux kernel that affects almost every distro of the Linux operating system, including Redhat, and Ubuntu.

Over a month back, a nine-year-old privilege-escalation vulnerability, dubbed “Dirty COW,” was discovered in the Linux kernel that affected every distro of the open-source operating system, including Red Hat,

Posted in Denial of Service, hacking news, how to hack linux, Linux hacking, Linux kernel, Linux kernel exploit, linux security, Linux Vulnerability, server hacking, Vulnerability | Comments (0)

Internet Traffic Hijacking Linux Flaw Affects 80% of Android Devices

August 16th, 2016

An estimated 80 percent of Android smartphones and tablets running Android 4.4 KitKat and higher are vulnerable to a recently disclosed Linux kernel flaw that allows hackers to terminate connections, spy on unencrypted traffic or inject malware into the parties’ communications.

Even the latest Android Nougat Preview is considered to be vulnerable.
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Posted in hacking news, how to hack android, Linux hacking, Linux kernel, linux security, TCP protocol, Vulnerability | Comments (0)

Critical glibc Flaw Puts Linux Machines and Apps at Risk (Patch Immediately)

February 17th, 2016
glibc-linux-flaw

A highly critical vulnerability has been uncovered in the GNU C Library (glibc), a key component of most Linux distributions, that leaves nearly all Linux machines, thousands of apps and electronic devices vulnerable to hackers that can take full control over them.

Just clicking on a link or connecting to a server can result in remote code execution (RCE), allowing hackers to steal credentials, spy on users, seize control of computers, and many more.
The vulnerability is similar to the last year’s GHOST vulnerability (CVE-2015-0235) that left countless machines vulnerable to remote code execution (RCE) attacks, representing a major Internet threat.
GNU C Library (glibc) is a collection of open source code that powers thousands of standalone apps and most Linux distributions, including those distributed to routers and other types of hardware.
The recent flaw, which is indexed as CVE-2015-7547, is a stack-based buffer overflow vulnerability in glibc’s DNS client-side resolver that is used to translate human-readable domain names, like google.com, into a network IP address.
The buffer overflow flaw is triggered when the getaddrinfo() library function that performs domain-name lookups is in use, allowing hackers to remotely execute malicious code.

How Does the Flaw Work?

The flaw can be exploited when an affected device or app make queries to a malicious DNS server that returns too much information to a lookup request and floods the program’s memory with code.
This code then compromises the vulnerable application or device and tries to take over the control over the whole system.
It is possible to inject the domain name into server log files, which when resolved will trigger remote code execution. An SSH (Secure Shell) client connecting to a server could also be compromised.
However, an attacker need to bypass several operating system security mechanisms – like ASLR and non-executable stack protection – in order to achieve successful RCE attack.
Alternatively, an attacker on your network could perform man-in-the-middle (MitM) attacks and tamper with DNS replies in a view to monitoring and manipulating (injecting payloads of malicious code) data flowing between a vulnerable device and the Internet.

Affected Software and Devices

All versions of glibc after 2.9 are vulnerable. Therefore, any software or application that connects to things on a network or the Internet and uses glibc is at RISK.
The widely used SSH, sudo, and curl utilities are all known to be affected by the buffer overflow bug, and security researchers warn that the list of other affected applications or code is almost too diverse and numerous to enumerate completely.
The vulnerability could extend to a nearly all the major software, including:
  • Virtually all distributions of Linux.
  • Programming languages such as the Python, PHP, and Ruby on Rails.
  • Many others that use Linux code to lookup the numerical IP address of an Internet domain.
  • Most Bitcoin software is reportedly vulnerable, too.

Who are Not Affected

The good news is users of Google’s Android mobile operating system aren’t vulnerable to this flaw. As the company uses a glibc substitute known as Bionic that is not susceptible, according to a Google representative.
Additionally, a lot of embedded Linux devices, including home routers and various gadgets, are not affected by the bug because these devices use the uclibc library as it is more lightweight than hefty glibc.
The vulnerability was first introduced in May 2008 but was reported to the glibc maintainers July 2015.
The vulnerability was discovered independently by researchers at Google and Red Hat, who found that the vulnerability has likely not been publicly attacked.
The flaw was discovered when one of the Google’s SSH apps experienced a severe error called a segmentation fault each time it attempted to contact to a particular Internet address, Google’s security team reported in a blog post published Monday.

Where glibc went Wrong

Google researchers figured out that the error was due to a buffer overflow bug inside the glibc library that made malicious code execution attacks possible. The researchers then notified glibc maintainers.
Here’s what went wrong, according to the Google engineers:

“glibc reserves 2048 bytes in the stack through alloca() for the DNS answer at _nss_dns_gethostbyname4_r() for hosting responses to a DNS query. Later on, at send_dg() and send_vc(), if the response is larger than 2048 bytes, a new buffer is allocated from the heap and all the information (buffer pointer, new buffer size and response size) is updated.”

“Under certain conditions a mismatch between the stack buffer and the new heap allocation will happen. The final effect is that the stack buffer will be used to store the DNS response, even though the response is larger than the stack buffer and a heap buffer was allocated. This behavior leads to the stack buffer overflow.”

Proof-of-Concept Exploit Released

Google bod Fermin J. Serna released a Proof-of-Concept (POC) exploit code on Tuesday.
With this POC code, you can verify if you are affected by this critical issue, and verify any mitigations you may wish to enact.

Patch glibc Vulnerability

Google researchers, working with security researchers at Red Hat, have released a patch to fix the programming blunder.
However, it is now up to the community behind the Linux OS and manufacturers, to roll out the patch to their affected software and devices as soon as possible.
For people running servers, fixing the issue will be a simple process of downloading and installing the patch update.
But for other users, patching the problem may not be so easy. The apps compiled with a vulnerable glibc version should be recompiled with an updated version – a process that will take time as users of affected apps have to wait for updates to become available from developers.
Meanwhile, you can help prevent exploitation of the flaw, if you aren’t able to immediately patch your instance of glibc, by limiting all TCP DNS replies to 1024 bytes, and dropping UDP DNS packets larger than 512 bytes.
For more in-depth information on the glibc flaw, you can read Red Hat blog post.

Posted in DNS hijacking, glibc, GNU C Library, Google Security, hacking news, Linux hacking, Linux OS, linux security, Programming, remote code execution, Vulnerability | Comments (0)

You can Hack into a Linux Computer just by pressing ‘Backspace’ 28 times

December 17th, 2015

So what would anyone need to bypass password protection on your computer?

It just needs to hit the backspace key 28 times, for at least the computer running Linux operating system.

Wait, what?

A pair of security researchers from the University of Valencia have uncovered a bizarre bug in several distributions of Linux that could allow anyone to bypass any kind of authentication during

Posted in GRUB bootloader, Grub password hacking, hacking linux, Linux Grub, linux grub install, linux security, Vulnerability | Comments (0)

Bug in OpenSSH Opens Linux Machines to Password Cracking Attack

July 23rd, 2015

A simple but highly critical vulnerability recently disclosed in the most widely used OpenSSH software allows attackers to try thousands of password login attempts per connection in a short period.

OpenSSH is the most popular software widely used for secure remote access to Linux-based systems. Generally, the software allows 3 to 6 Password login attempts before closing a connection, but a

Posted in brute force attack, dictionary attack, hack ssh password, hacking news, linux security, Linux Vulnerability, OpenSSH, password hacking, SSH password cracking, ssh security, Vulnerability | Comments (0)

Enterprise Apps in Scope of Ghost glibc Vulnerability

February 6th, 2015

Researchers at Veracode examined whether enterprise applications were also vulnerable to the Ghost vulnerability in glibc.

Posted in Bash, Chris Wysopal, enterprise applications, GHOST vulnerability, glibc, linux security, Open Source Security, PHP, Qualys, Sucuri, Veracode, vulnerabilities, Web Security, WordPress | Comments (0)