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HighVulnerabilityCVE-2026-109089updated 27 Oct 2026, 21:16 UTC

libXi (X Input library) can overflow memory when a malicious X server sends crafted data

A small library many Linux desktop programs use to read mouse and keyboard input can be tricked into writing past the memory it reserved. A harmful display server could use this to crash programs or possibly run its own code.

Fixed in libXi 1.8.4 or laterOfficial, 2 sources
SeverityHighCVSS 7.5 of 10
Being exploited?Not knownNo attacks reported so far
Fix available?YeslibXi 1.8.4 or later · since 27 Oct 2026
How sure is this?Official, 2 sourcesBacked by an official source

How the attack works simplified

  1. 1Malicious X serverAttacker controls or impersonates the display server
  2. 2Sends crafted dataDEVICE_RESOLUTION message with oversized content
  3. 3libXi parses dataMissing bounds check when handling the message
  4. 4Heap overflowMemory written past its allocated boundary
  5. ResultApplication crashes or may be compromised

What happened

A heap buffer overflow exists in libXi's handling of DEVICE_RESOLUTION data before version 1.8.4, triggered by a malicious X server.

Why it is dangerous: Attackers controlling or impersonating an X server could crash or potentially compromise applications using libXi, which affects Linux and Unix desktop users and software.

Are you affected?

You are affected if you use libXi older than 1.8.4 and connect to an X server you do not fully trust.

libXi before 1.8.4

What to do

  1. Update libXi to version 1.8.4 or later using your system's package manager
  2. Only connect your graphical session to X servers you trust
  3. Check your distribution's advisories for packaged fixes

Timeline

  1. 27 Oct 2026, 17:16 UTC
    Publicly disclosed
  2. 27 Oct 2026, 17:16 UTC
    Reported by NVD · NVD
  3. 27 Oct 2026, 17:20 UTC
    Picked up by Zero Radar
  4. 27 Oct 2026, 21:16 UTC
    oss-security reported on it · oss-security

Sources 2 reports, oldest first

Official vendor, government CERT or advisory database

Security researchers research teams and mailing lists

Technical details

ID
CVE-2026-109089
CVSS
7.5 / 10
EPSS
0.3% chance of exploitation within 30 days
Disclosed
27 Oct 2026, 17:16 UTC
On Zero Radar
27 Oct 2026, 17:20 UTC (4 min after disclosure)
Last change
27 Oct 2026, 21:16 UTC

The plain-language parts and the attack diagram were written by an AI model (anthropic/claude-haiku-5.5) from the sources above. Facts like versions, exploitation and dates come from the sources themselves. How Zero Radar works

libXi (X Input library) can overflow memory when a malicious X server sends crafted data · Zero Radar