Ubuntu LinuxOperating system · Canonical
CVE-2018-6307
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 ca2a5ac02fbbadd0a21fabba779c1ea69173d10b contains heap use-after-free vulnerability in server code of file transfer extension 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 use-after-free vulnerability in the server-side file transfer extension. The flaw exists before commit ca2a5ac02fbbadd0a21fabba779c1ea69173d10b and can allow remote attackers to execute arbitrary code by exploiting freed memory references during file transfer operations.
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
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.0/AV:N/AC:H/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 LibVNC versionRun 'dpkg -l libvncserver*' on Debian/Ubuntu systems, or check the library version directly with 'strings /usr/lib/*/libvncserver.so* | grep -i version' or examine the binary linked by the VNC server processAffected if Version is below 0.9.12 (or unknown/unable to determine version)
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Confirm VNC server process is using libvncserverIdentify running VNC server processes and check which library they link to using 'ps aux | grep vnc' combined with 'ldd -r <vnc_binary>' or check for listening VNC ports with 'netstat -tulpn | grep -E "59[0-9][0-9]"'Affected if A VNC server process is running and linked to libvncserver
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Verify file transfer extension is enabledExamine VNC server configuration files (often in /etc/vnc or ~/.vnc) and running process arguments for file transfer settings. In code, this feature is typically controlled by rfbAllowFileTransfer() or similar functions in the configurationAffected if File transfer capability is explicitly enabled or accessible to clients
Environment is affected if running libvncserver with a version prior to 0.9.12 AND the file transfer extension is enabled in the VNC server configuration.
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
Update LibVNC to a version incorporating commit ca2a5ac02fbbadd0a21fabba779c1ea69173d10b or later, which contains the fix for the use-after-free vulnerability in the file transfer extension.
Fix this in Ubuntu Linux
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,096.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-6307 — 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-2018-6307 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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A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- 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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