Debian LinuxOperating system · Debian
CVE-2018-20023
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 8b06f835e259652b0ff026898014fc7297ade858 contains CWE-665: Improper Initialization vulnerability in VNC Repeater client code that allows attacker to read stack memory and can be abuse for information disclosure. Combined with another vulnerability, it can be used to leak stack memory layout and in bypassing ASLR
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 before 8b06f835e259652b0ff026898014fc7297ade858 contains an improper initialization vulnerability (CWE-665) in the VNC Repeater client code. The flaw allows attackers to read stack memory, leading to information disclosure. When chained with other vulnerabilities, this can leak stack memory layout and facilitate ASLR bypass.
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
Debian LinuxOperating system
= 8.0= 9.0
Ubuntu LinuxOperating system
= 14.04= 16.04= 18.04= 18.10< 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
- None
- Availability
- None
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
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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Check installed LibVNC versionIdentify the installed version of libvncserver or libvnc on the system. On Linux systems, this can often be done via package manager (dpkg -l libvncserver or rpm -q libvncserver) or by checking the library version file. Compare the version found to the affected range: versions before 0.9.12 are vulnerable.Affected if The installed version is libvncserver or libvnc earlier than version 0.9.12
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Determine if VNC Repeater client feature is in useInspect the VNC client configuration or running processes to determine whether the VNC Repeater client functionality is enabled or being used. This may involve reviewing VNC client configuration files, startup scripts, or process parameters.Affected if The VNC Repeater client feature is actively configured or in use on the system
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Verify operating system version (Debian/Ubuntu)Check the installed operating system version. For Debian, run 'cat /etc/debian_version'. For Ubuntu, run 'lsb_release -a' or check /etc/lsb-release. Compare against the affected versions: Debian 8.0 and 9.0, Ubuntu 14.04, 16.04, 18.04, and 18.10.Affected if The system is running Debian 8.0, Debian 9.0, Ubuntu 14.04, Ubuntu 16.04, Ubuntu 18.04, or Ubuntu 18.10 with a vulnerable LibVNC installation
You are affected if you have LibVNC (libvncserver) version earlier than 0.9.12 AND the VNC Repeater client feature is enabled or in use on your system.
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.
From vendor data0.9.12
Upgrade LibVNC to version 8b06f835e259652b0ff026898014fc7297ade858 or later to obtain the fix for the improper initialization in the VNC Repeater client code.
Fix this in Debian Linux
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-20023 — 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-2018-20023 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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