Ubuntu LinuxOperating system · Canonical
CVE-2018-20020
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedLibVNC before commit 7b1ef0ffc4815cab9a96c7278394152bdc89dc4d contains heap out-of-bound write vulnerability inside structure in VNC client code that can result remote code execution
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceLibVNC contains a heap out-of-bounds write vulnerability in the VNC client code (before commit 7b1ef0ffc4815cab9a96c7278394152bdc89dc4d). The flaw exists within a structure in the client implementation and can allow remote code execution via specially crafted VNC server responses.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Ubuntu LinuxOperating system
= 14.04= 16.04= 18.04= 18.10
Debian LinuxOperating system
= 8.0= 9.0< 0.9.12CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify installed Libvncserver packageRun 'dpkg -l | grep libvnc' on Debian/Ubuntu, or 'rpm -qa | grep vnc' on RHEL-based systems, or check for libvncclient.so files with 'find /usr -name "*libvnc*" 2>/dev/null'Affected if Libvncserver or libvncclient is installed with version below 0.9.12
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Check LibVNC client library versionIf library files exist, run 'strings libvncclient.so | grep -i version' or check the soname with 'readelf -d libvncclient.so | grep SONAME' and compare against 0.9.12Affected if The library version is less than 0.9.12 or cannot be determined to be 0.9.12 or later
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Identify applications using VNC client codeSearch for binaries that link against libvncclient: 'ldd /path/to/binary | grep vnc' or check running processes that may function as VNC viewersAffected if Any VNC client application is running against the vulnerable library
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Verify git commit of LibVNC source (if compiled from source)If using source-built LibVNC, check git log for the commit hash: 'git log --oneline -1' in the source directory and compare to 7b1ef0ffc4815cab9a96c7278394152bdc89dc4dAffected if The source commit precedes 7b1ef0ffc4815cab9a96c7278394152bdc89dc4d
The environment is affected if Libvncserver/client version is below 0.9.12 (or source commit is before 7b1ef0ffc4815cab9a96c7278394152bdc89dc4d) and any VNC client functionality is in use.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped0.9.12
Update LibVNC to the patched version (commit 7b1ef0ffc4815cab9a96c7278394152bdc89dc4d or later) to remediate the heap overflow vulnerability.
LibVNCServer 0.9.12 or later
- Update the package list: sudo apt-get update
- Upgrade libvncserver to the latest version: sudo apt-get install --upgrade libvncserver1 (or libvncclient)
- Verify the installed version is 0.9.12 or later: dpkg -l | grep libvncserver
- Restart any VNC services using the library after upgrade
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Ubuntu Linux
Scoped from the published advisory
- Consultation4.0 h
- Implementation4.0 h
- Testing8.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,504.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-20020 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2018-20020 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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