Description
A critical vulnerability has been identified in the login program for System V based operating systems. Specifically, this buffer overflow vulnerability, notified as CVE-2001-0797, allows remote attackers to execute arbitrary commands by sending a large number of arguments through services such as telnet and rlogin.
Affected Product(s)
- Solaris (version not specified)
- HP-UX 10.00 and 10.01
Technical Details
The buffer overflow vulnerability identified as CVE-2001-0797 exists in the login program (/bin/login) used in various System V based operating systems like Solaris, HP-UX, AIX, SGI, and Unixware. This vulnerability arises due to improper handling of environment variables passed during the authentication process within login sessions controlled by services such as telnet and rlogin.
An attacker can exploit this flaw by sending a large number of arguments to the login program. Since /bin/login runs with elevated privileges to authenticate users, exploiting this vulnerability allows attackers to execute arbitrary commands with those privileges. It predominantly involves overwhelming the buffer memory allocated for environment variables, causing it to overflow and allowing the insertion of malicious code.
The vulnerability affects multiple vendors and versions of operating systems derived from System V Unix, including but not limited to Solaris, HP-UX, AIX, SGI, and Unixware. The /bin/login utility in these systems can be stimulated through remote logins via telnet and rlogin services. Additionally, certain SSH configurations which use /bin/login can also be leveraged for exploitation.
Several references highlight the severity of the issue. For instance, SecurityFocus reported on the inherent risks associated with this vulnerability, while CERT and Cisco detailed the implications of remote exploitation, such as unauthorized command execution on the affected systems. Adversaries have capitalized on this vulnerability by crashing /bin/login remotely through services like telnet, which leads to remote code execution.
These types of services are often enabled by default, thereby escalating the risk associated with CVE-2001-0797. Notably, patches and updates have been released to address this vulnerability, requiring users to upgrade their systems to versions that mitigate the risk or apply specific workarounds. Many organizations have released advisories detailing the steps to mitigate this vulnerability, emphasizing the importance of timely updates and secure configuration practices.
Various plugins identify and attempt to exploit this vulnerability. For instance, plugins associated with Nessus and Metasploit have detailed scripts to simulate attacks and validate the presence of the vulnerability in /bin/login by sending excessive environment variables and observing the crash behaviour. These tools provide penetration testers and security analysts with the means to assess the susceptibility of their systems.
In practice, fixing this vulnerability often involves upgrading to a patched version, modifying telnet and rlogin service configurations, or completely disabling telnet and rlogin services in favour of more secure alternatives like SSH that do not rely on the vulnerable /bin/login for authentication.
Overall, this vulnerability demonstrates a critical intersection of outdated authentication processes and emerging security concerns, highlighting the need for keeping systems regularly updated and recognizing the security implications associated with legacy protocols and services.
Weakness
The weakness associated with this vulnerability is classified as CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer. This type of weakness occurs when an application performs operations on a memory buffer, but it does not verify that the operations stay within the bounds of that buffer. This results in a buffer overflow condition.
Impact Assessment
If this vulnerability is exploited, it could allow an attacker to gain unauthorized access to sensitive data or execute arbitrary code on the affected system. This could lead to a full system compromise, including unauthorized access to remote systems, database breaches, and the potential for privilege escalation attacks. Systems that rely on telnet and rlogin services are particularly at risk if not adequately secured or updated.
Active Exploitation
We have observed activity from the adversary group Equation Group, which is known for targeting similar vulnerabilities in the past. Exploitation examples include:
- Sun Login Overflow
- Sun Login pamh Overflow
- System V Derived /bin/login – Extraneous Arguments Buffer Overflow (modem based) (Metasploit)
- Solaris TelnetD – ‘TTYPROMPT’ Remote Buffer Overflow (2) (Metasploit)
- System V Derived /bin/login – Extraneous Arguments Buffer Overflow (Metasploit)
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Ransomware Association
The vulnerability has been linked to ransomware attacks, specifically when adversaries use the exploit to gain initial access to the system. These exploits can facilitate the creation of a foothold in the network, further leading to the deployment of ransomware. The Equation Group has reportedly utilized this attack vector for such purposes.
Mitigation and Resolution
We have released a patch that addresses this vulnerability. Please update to the following patched versions immediately: Patch 1, Patch 2, Workaround 1. Ensure that all relevant services such as telnet and rlogin are either securely configured or disabled if they are not necessary.
Recommendations
- We strongly recommend that all customers apply the latest patch as soon as possible.
- Upgrade your systems to the versions that include the patch fix.
- Disable unnecessary services such as telnet and rlogin to mitigate attack vectors.
- Regularly monitor and secure remote login services.
- Consider configuring SSH for secure remote access and ensuring it does not use /bin/login.
- Implement network security measures to detect and prevent buffer overflow attacks.
- Perform regular system updates and security audits.
Referencesย
- Cisco Security Advisory
- CVE Details
- NVD Detail
- SGI Advisory
- Caldera Advisory
- Bugtraq Post
- SunSolve Bulletin
- IBM Support
- CERT Advisory
- CERT Vuln Notes
- SecurityFocus Archive
- SecurityFocus BID
- ISS Alert
- X-Force Vulnerability
- OVAL Repository