Critical Memory Write Vulnerability in libssh2: CVE-2019-3863
Summary
ALPINE-CVE-2019-3863: A flaw was found in libssh2 before 1.8.1. Affects libssh2 versions < 1.8.1-r0. Fixed in 1.8.1-r0. 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 enables secure communication over unsecured networks by providing encryption, authentication, and data integrity. This library is essential for applications that require secure file transfers and remote command execution. However, a flaw in libssh2 versions prior to 1.8.1 exposes it to a critical vulnerability that can lead to severe security risks.
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 execute arbitrary code, crash the application, or gain unauthorized access to sensitive data. The vulnerability is classified with a CVSS score of 8.8, indicating a high severity level.
How To Fix
Minimum fixed version
1.8.1-r0
This is the first release that contains the fix.
sudo apk add --upgrade libssh2Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
If updating the package is not immediately feasible, consider implementing strict input validation to limit the length of keyboard interactive response messages. This can help mitigate the risk of exploitation until the package can be updated.
Conclusion
The CVE-2019-3863 vulnerability in libssh2 poses a significant risk due to its potential for out-of-bounds memory writes. It is crucial for users of the library to update to the patched version 1.8.1-r0 or later to mitigate these risks. Utilizing tools like Vulert can help monitor and alert 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 the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without needing to sign up.
The vulnerability can lead to arbitrary code execution, application crashes, or unauthorized access to sensitive data, posing significant security risks.
Yes, the patch is available in libssh2 version 1.8.1-r0 and later. Updating to this version will resolve the vulnerability.
If immediate updates are not possible, implement strict input validation to limit the length of keyboard interactive response messages as a temporary workaround.
References
Related vulnerabilities
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