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FedoraOperating system · Fedoraproject

CVE-2016-7950

CRITICAL · 9.8 CVSS v3.0 Published 2016-12-13
Fix available
A fix is available. Upgrade to after 0.9.9 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

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 · unedited
The XRenderQueryFilters function in X.org libXrender before 0.9.10 allows remote X servers to trigger out-of-bounds write operations via vectors involving filter name lengths.

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 confidence

CVE-2016-7950 is a buffer overflow vulnerability in the XRenderQueryFilters function of X.org libXrender (versions prior to 0.9.10). A malicious remote X server can send specially crafted filter name lengths that trigger out-of-bounds write operations on the connected client, potentially allowing arbitrary code execution with the privileges of the X client application.

MitigationUpdate libXrender to version 0.9.10 or later to obtain the fix. If immediate patching is not feasible, restrict X server connections to trusted sources or disable the Xrender extension in untrusted environments.

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
FedoraOperating system
Affected:= 24= 25
LibxrenderApplication
Affected:<= 0.9.9

CVSS 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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify the installed libXrender package version
    On Fedora-based systems: rpm -qa | grep libXrender. On Debian-based: dpkg -l | grep libxrender. On general Linux: ls -la /usr/lib*/libXrender* or check your package manager for libxrender.
    Affected if The installed version is less than 0.9.10 (e.g., 0.9.9 or earlier)
  2. Verify if the Xrender extension is loaded
    Run 'xdpyinfo' or check X server logs for the presence of the RENDER extension. Alternatively, inspect /var/log/Xorg.0.log for 'RENDER' or 'Xrender' references.
    Affected if The RENDER extension is actively loaded and used by applications
  3. Determine if X server accepts remote connections
    Check the X server configuration: run 'xdpyinfo' and look at the 'number of screens' output, or check /etc/X11/xdm/xdm-config and /etc/gdm/custom.conf for 'DisallowTCP=false' settings. Also check if xhost is enabled: 'xhost' command shows + (allowing remote connections).
    Affected if The X server is configured to accept TCP connections from remote hosts (DisallowTCP=false or xhost +)
  4. Confirm the vulnerability trigger condition
    The flaw is triggered when a client connects to a malicious X server that sends specially crafted filter name lengths. Check if any X clients are connecting to untrusted or network-accessible X servers.
    Affected if Clients connect to untrusted or publicly accessible X servers

A system is affected if it runs libXrender version 0.9.9 or earlier AND has the Xrender extension enabled with potential exposure to untrusted X servers.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Upgrade available Upgrade to a release after 0.9.9
Interim mitigation

Update libXrender to version 0.9.10 or later to obtain the fix. If immediate patching is not feasible, restrict X server connections to trusted sources or disable the Xrender extension in untrusted environments.

Recommended fix High confidence

libXrender 0.9.10 or later

  1. 1. Check the current version of libxrender installed: `rpm -qa | grep libxrender`
  2. 2. Update the package using the Fedora package manager: `sudo dnf update libxrender` or `sudo yum update libxrender`
  3. 3. Verify the updated version is 0.9.10 or later: `rpm -qa | grep libxrender`
  4. 4. Restart X server or reboot the system to ensure the updated library is loaded
Caveat Library upgrade typically has minimal breaking changes; verify X server functionality after upgrade

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Fedora Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,080
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2016-7950 in production — separate from our analysis above.

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What this is

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.

What belongs here
  • 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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