dbcve.org
Enterprise LinuxOperating system · Redhat

CVE-2023-43786

MEDIUM · 5.5 CVSS v3.1 Published 2023-10-10
Fix available
A fix is available. Upgrade to 1.8.7 or later.
See remediation →
57/100
Remediation priority · Elevated
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
A vulnerability was found in libX11 due to an infinite loop within the PutSubImage() function. This flaw allows a local user to consume all available system resources and cause a denial of service condition.

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 · moderate confidence

A vulnerability in libX11's PutSubImage() function contains an infinite loop that can be triggered by a local user, causing excessive resource consumption and resulting in a denial of service condition.

MitigationApply the vendor-supplied patch or update libX11 to the patched version to resolve the infinite loop in PutSubImage().

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
Enterprise LinuxOperating system
Affected:= 8.0= 9.0
FedoraOperating system
Affected:= 38
Libx11Application
Affected:< 1.8.7

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
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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 installed libX11 version
    Run 'rpm -q libX11' on RHEL/Fedora, or 'dpkg -l libx11-dev' on Debian/Ubuntu, or check the library file directly with 'strings /usr/lib/x86_64-linux-gnu/libX11.so.6 | grep "^1\." | tail -1'
    Affected if The reported version is less than 1.8.7, or the package version matches RHEL 8.0, RHEL 9.0, or Fedora 38 without the security patch applied
  2. Verify X11 display server is in use
    Check for running X server or active DISPLAY variable: run 'echo $DISPLAY' or 'ps aux | grep -E "Xorg|Xwayland" | grep -v grep'
    Affected if An X11 environment is active; the vulnerable PutSubImage() function is called by X clients when rendering images to the display server
  3. Identify applications using libX11 rendering
    List processes that link to libX11: run 'lsof -p $(pgrep -f "^[^"]*X11[^"]*$") 2>/dev/null | grep libX11 || ss -tlxp | grep "x11"' to find active X clients
    Affected if Any X client application is running that performs image rendering operations; the vulnerability triggers specifically when PutSubImage() is invoked during subimage transfer operations

You are affected if libX11 version is below 1.8.7 (or matches the unpatched RHEL 8.0/9.0 or Fedora 38 packages) AND an X11 environment with active graphical applications is in use, allowing the infinite loop in PutSubImage() to be triggered during image rendering.

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 1.8.7 or later
Fixed in 1.8.7
Interim mitigation

Apply the vendor-supplied patch or update libX11 to the patched version to resolve the infinite loop in PutSubImage().

Recommended fix Moderate confidence

libx11 version 1.8.7 or later

  1. Identify the libx11 package installed on your system using your distribution's package manager (e.g., rpm -qa | grep libx11, dpkg -l | grep libx11, or dnf list installed | grep libx11)
  2. Update the libx11 package to version 1.8.7 or later using your distribution's package manager: For RHEL/CentOS/Enterprise Linux: dnf update libx11 or yum update libx11
  3. For Fedora: dnf update libx11
  4. For Debian/Ubuntu: apt update && apt install libx11-6
  5. Restart any applications that use libX11 to ensure the updated library is loaded
  6. Verify the installed version matches or exceeds 1.8.7 using: rpm -q libx11 or dpkg -s libx11-6

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

Fix this in Enterprise Linux Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,390
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Scan for this in your stack

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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-2023-43786 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
  • No spam, self-promotion, credentials, or personal data