Critical Buffer Overflow Vulnerability in libvncserver: CVE-2016-9942
Summary
ALPINE-CVE-2016-9942: Heap-based buffer overflow in ultra.c in LibVNCClient in LibVNCServer before 0.9.11 allows remote servers to cause a denial of service (application crash) or possibly execute arbitrary code via a crafted FramebufferUpdat... Affects libvncserver versions < 0.9.11-r0. Fixed in 0.9.11-r0. How to fix ↓
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Background
libvncserver is an open-source library that enables the implementation of VNC (Virtual Network Computing) server functionality. It allows users to remotely control another computer's desktop environment. The library is widely used in various applications that require remote desktop access. However, it has been found to be vulnerable to a critical buffer overflow issue, which can lead to severe security risks if not addressed.
Vulnerability Detail
The vulnerability, identified as CVE-2016-9942, is a heap-based buffer overflow located in the ultra.c file of the LibVNCClient component of libvncserver. This flaw allows remote servers to send crafted FramebufferUpdate messages with an Ultra type tile, causing the decompressed length of the LZO payload to exceed the specified tile dimensions. This can lead to application crashes or potentially allow attackers to execute arbitrary code, posing a significant threat to system integrity and confidentiality.
How To Fix
Minimum fixed version
0.9.11-r0
This is the first release that contains the fix.
sudo apk add --upgrade libvncserverTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
If immediate patching is not feasible, consider implementing network-level security measures such as firewalls to restrict access to the VNC server. Additionally, monitor logs for unusual activity that may indicate exploitation attempts.
Conclusion
The CVE-2016-9942 vulnerability in libvncserver poses a significant risk due to its potential for remote code execution and application crashes. It is crucial for users to update to the latest patched versions of the library to safeguard their systems. Utilizing tools like Vulert can aid in monitoring for such vulnerabilities effectively.
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FAQ
CVE-2016-9942 is a critical buffer overflow vulnerability in the libvncserver library that can lead to application crashes or arbitrary code execution.
You can use the Vulert platform to monitor and alert for open-source vulnerabilities in your software by simply using a manifest file like package-lock.json.
The CVSS score for CVE-2016-9942 is 9.8, indicating a critical level of severity.
Exploitation of this vulnerability can lead to denial of service or unauthorized remote code execution, compromising system security.
Yes, implementing network security measures such as firewalls and monitoring for unusual activity can help mitigate risks until a patch is applied.
References
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