Buffer Overflow Vulnerability in OpenVPN-Auth-LDAP Package
Summary
DEBIAN-CVE-2024-28820: Buffer overflow in the extract_openvpn_cr function in openvpn-cr.c in openvpn-auth-ldap (aka the Three Rings Auth-LDAP plugin for OpenVPN) 2.0.4 allows attackers with a valid LDAP username and who can control the challen... Affects openvpn-auth-ldap versions < 2.0.4-4. Fixed in 2.0.4-4. How to fix ↓
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Background
OpenVPN-Auth-LDAP is a plugin for OpenVPN that facilitates authentication via LDAP directories. This package is designed to enhance the security of VPN connections by allowing organizations to manage user credentials through their existing LDAP infrastructure. However, the package has a critical vulnerability that can be exploited by attackers with valid LDAP usernames, potentially compromising the security of the VPN.
Vulnerability Detail
The vulnerability arises from a buffer overflow in the extract_openvpn_cr function located in openvpn-cr.c. This flaw allows attackers, who possess a valid LDAP username and can manipulate the challenge/response password field, to input a string containing more than 14 colons. Such an input can lead to a buffer overflow, which may allow an attacker to execute arbitrary code or crash the application, thereby compromising the integrity and availability of the VPN service.
How To Fix
Minimum fixed version
2.0.4-4
This is the first release that contains the fix.
sudo apt-get install --only-upgrade openvpn-auth-ldapTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, it is advisable to restrict access to the LDAP authentication mechanism for users who do not require it. Additionally, monitoring the input fields for excessive characters can help mitigate the risk until a proper patch is applied.
Conclusion
The buffer overflow vulnerability in the OpenVPN-Auth-LDAP package poses a significant risk to users relying on this authentication method. Immediate action is required to update the package to the patched version to ensure the security of VPN connections. Utilizing tools like Vulert can help monitor and manage vulnerabilities effectively.
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FAQ
A buffer overflow occurs when data exceeds the storage capacity of a buffer, leading to adjacent memory being overwritten. This can result in unpredictable behavior, crashes, or security vulnerabilities.
Attackers with valid LDAP usernames who can control the challenge/response password field can exploit this vulnerability.
Exploiting this vulnerability can lead to arbitrary code execution, application crashes, or unauthorized access to sensitive information within the VPN.
You can use Vulert, which monitors open-source vulnerabilities in your software. By uploading your manifest file, such as package-lock.json, you can receive real-time alerts about vulnerabilities, including this one.
While waiting for a patch, restrict access to the LDAP authentication mechanism and validate input fields to prevent excessive characters from being processed.
References
Related vulnerabilities
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