Memory Write Error in libssh2: CVE-2019-3863 Vulnerability Overview
Summary
DEBIAN-CVE-2019-3863: A flaw was found in libssh2 before 1.8.1. Affects libssh2 versions < 1.8.0-2.1. Fixed in 1.8.0-2.1. How to fix ↓
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Background
libssh2 is a widely used library that provides an API for implementing SSH2 client functionality in applications. It is essential for secure communication over networks, enabling features such as file transfer and remote command execution. However, prior to version 1.8.1, libssh2 had a critical vulnerability that could lead to memory corruption, impacting the security and stability of applications relying on this library.
Vulnerability Detail
A flaw was found in libssh2 before version 1.8.1, where a server could send multiple keyboard interactive response messages whose total length exceeds the maximum value of an unsigned char. This flaw can lead to an out-of-bounds memory write error, potentially allowing an attacker to exploit the vulnerability to execute arbitrary code or crash the application. The vulnerability arises from improper handling of input lengths, making it crucial for users to address it promptly.
How To Fix
Minimum fixed version
1.8.0-2.1
This is the first release that contains the fix.
sudo apt-get install --only-upgrade libssh2Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, users can limit the input length of keyboard interactive responses or implement additional validation checks in their applications to prevent excessive input from being processed. However, updating to the patched version is the recommended solution.
Conclusion
The CVE-2019-3863 vulnerability in libssh2 poses a significant risk due to its potential for memory corruption. Users are strongly encouraged to update their libssh2 packages to the latest version to ensure their applications remain secure. Utilizing tools like Vulert can help monitor for such vulnerabilities in real-time.
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FAQ
CVE-2019-3863 is a vulnerability in the libssh2 library that allows for out-of-bounds memory writes due to improper handling of keyboard interactive response messages.
You can use Vulert's playground at Vulert Scanner to check if your application is affected by this vulnerability without needing to sign up.
Exploiting this vulnerability could lead to arbitrary code execution or application crashes, compromising the security and stability of affected systems.
Yes, the vulnerability is fixed in libssh2 version 1.8.0-2.1 and later. Users are advised to update to this version or newer.
If immediate updates are not possible, consider implementing input validation to mitigate the risk until you can apply the patch.
References
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