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Ubuntu LinuxOperating system · Canonical

CVE-2013-1981

MEDIUM · 6.8 CVSS v2.0 Published 2013-06-15
Fix available
A fix is available. Upgrade to after 1.5.99.901 or later.
See remediation →
77/100
Remediation priority · High
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
Multiple integer overflows in X.org libX11 1.5.99.901 (1.6 RC1) and earlier allow X servers to trigger allocation of insufficient memory and a buffer overflow via vectors related to the (1) XQueryFont, (2) _XF86BigfontQueryFont, (3) XListFontsWithInfo, (4) XGetMotionEvents, (5) XListHosts, (6) XGetModifierMapping, (7) XGetPointerMapping, (8) XGetKeyboardMapping, (9) XGetWindowProperty, (10) XGetImage, (11) LoadColornameDB, (12) XrmGetFileDatabase, (13) _XimParseStringFile, or (14) TransFileName functions.

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

Multiple integer overflow vulnerabilities exist in libX11's font querying, window property retrieval, and resource database parsing functions. These flaws allow a malicious X server to provide specially crafted responses that cause insufficient memory allocation followed by buffer overflows in the client application.

MitigationUpdate libX11 to version 1.6.0 or later which contains the security patches. As a defense-in-depth measure, restrict X server connections to trusted sources and disable X11 forwarding in SSH when not required.

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
Affected:= 10.04= 12.04= 12.10= 13.04
Libx11Application
Affected:<= 1.5.99.901= 1.5.0

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
M
Authentication
None
Confidentiality
Partial
Integrity
Partial
Availability
Partial

AV:N/AC:M/Au:N/C:P/I:P/A:P

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 library version
    Run 'dpkg -l libx11-6' on Debian/Ubuntu systems, or 'rpm -q libX11' on Red Hat-based systems, or examine the library file directly with 'ls -la /usr/lib/*/libX11.so*' or 'ldconfig -p | grep libX11'
    Affected if The version displayed is 1.5.0 or any version <= 1.5.99.901 (including development releases) rather than 1.6.0 or later
  2. Check if X11 forwarding is enabled in SSH configuration
    Inspect /etc/ssh/sshd_config for 'X11Forwarding yes' entries and review user-specific SSH config files in ~/.ssh/config
    Affected if X11Forwarding is set to yes and the system uses SSH to connect to remote hosts, as this enables connections to potentially untrusted X servers
  3. Verify X server connection settings
    Check for XDMCP configuration in /etc/gdm/custom.conf or /etc/x11/gdm/gdm.conf, and review display manager settings that allow remote X connections
    Affected if The system is configured to accept remote X connections (XDMCP enabled, firewall allows port 6000+) or connects to untrusted X servers
  4. Identify applications using libX11
    Run 'ldd /usr/bin/* 2>/dev/null | grep libX11' to list executables linked against libX11, or check specific critical applications
    Affected if Multiple client applications dynamically link to libX11 and may be used to connect to X servers, increasing attack surface

The environment is affected if libX11 version 1.5.0 or any version <= 1.5.99.901 is installed AND the system runs X11 applications or enables X11 forwarding that could connect to potentially 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.

From vendor data
Upgrade available Upgrade to a release after 1.5.99.901
Interim mitigation

Update libX11 to version 1.6.0 or later which contains the security patches. As a defense-in-depth measure, restrict X server connections to trusted sources and disable X11 forwarding in SSH when not required.

Fix this in Ubuntu Linux Scoped from the published advisory
  • Consultation2.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA3.0 h
19.0 hours of engineering $3,280
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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-2013-1981 in production — separate from our analysis above.

No notes yet

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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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