LiveActive security incident?Get immediate response
CVE Record

CVE-2016-7943: The XListFonts function in X.org libX11 before 1.6.4 might allow remote X servers to gain privileges via ve...

The XListFonts function in X.org libX11 before 1.6.4 might allow remote X servers to gain privileges via vectors involving length fields, which trigger out-of-bounds write operations.

UnknownCVSS not scoredNot KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This is a flaw in X.org libX11 font-list handling. If an application using an older libX11 connects to a malicious or compromised X server, crafted font response length fields could corrupt client memory and potentially let that server gain the client's privileges. It mainly affects legacy Linux or Unix GUI environments, not typical web-facing services.

Executive priority

Treat this as a targeted legacy-platform risk. It deserves remediation in environments that still rely on X11, especially where users connect to remote X servers. It is lower urgency for systems without X11 clients or remote X workflows, and the bundle provides no active-exploitation evidence.

Technical view

CVE-2016-7943 affects XListFonts in X.org libX11 before 1.6.4. The source bundle describes improper handling of length fields that can trigger out-of-bounds writes. The documented attacker role is a remote X server influencing a connected X client. Vendor advisories indicate distribution updates were issued.

Likely exposure

Systems are exposed where libX11 older than 1.6.4 remains installed and X clients connect to untrusted, compromised, or remote X servers. Exposure is most plausible in older desktop fleets, X11 forwarding workflows, thin-client environments, or legacy Unix/Linux applications using Xlib.

Exploitation context

The bundle does not show CISA KEV listing or confirmed active exploitation. The plausible attack path requires a malicious or compromised X server interacting with a vulnerable X client, so this is not a generic unauthenticated internet service issue based on the provided evidence.

Researcher notes

The key evidence is the CVE description, X.Org advisory, and upstream libX11 commit. The affected range is stated only as libX11 before 1.6.4 in the bundle. No CVSS, CWE, proof of exploitation, or detailed product matrix is provided, so validation should rely on package inventory and vendor advisories.

Mitigation direction

  • Upgrade libX11 to version 1.6.4 or a vendor-patched package.
  • Apply relevant Ubuntu, Gentoo, Fedora, or other distribution security updates.
  • Avoid connecting X clients to untrusted remote X servers.
  • Review legacy X11 forwarding and thin-client workflows for vulnerable endpoints.
  • Check current vendor guidance where package status is unclear.

Validation and detection

  • Inventory installed libX11 package versions across Linux and Unix endpoints.
  • Confirm vulnerable systems are upgraded beyond libX11 1.6.4 or vendor-patched builds.
  • Identify workflows using remote X servers or X11 forwarding.
  • Prioritize privileged or sensitive X clients that may contact remote X servers.
  • Document exceptions where legacy systems cannot be patched immediately.
Prepared
Confidence
medium
Sources
8

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cve · low confidence lookup

CVE-2016-7943 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
7Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.