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Fencer Intel
high 7.5

CVE-2026-88806 json

libX11 XkbGetMap Reply Heap-based Buffer Overflow

published last mo. modified last mo. also EUVD-2026-83914

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 10%
public exploits
0
none known

Summary

A malicious X server could exploit a buffer overflow in libX11 before 1.8.14 during handling of XkbGetMap overflowing the key_sym_map.

Patch / fix

  • x.org libX11 1.8.14
  • libx11 Debian 14 2:1.8.14-1

debian advisories DEBIAN-CVE-2026-88806

  • libx11 Ubuntu 22.04 LTS 2:1.7.5-1ubuntu0.4
  • libx11 Ubuntu 24.04 LTS 2:1.8.7-1ubuntu0.1
  • libx11 Ubuntu 26.04 LTS 2:1.8.13-1ubuntu0.1
  • libx11 Ubuntu Pro 14.04 LTS 2:1.6.2-1ubuntu2.1+esm6
  • libx11 Ubuntu Pro 16.04 LTS 2:1.6.3-1ubuntu2.2+esm5
  • libx11 Ubuntu Pro 18.04 LTS 2:1.6.4-3ubuntu0.4+esm3
  • libx11 Ubuntu Pro 20.04 LTS 2:1.6.9-2ubuntu1.6+esm1

ubuntu advisories UBUNTU-CVE-2026-88806

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • libX11 Linux Micro 6.1 1.8.7-slfo.1.1_4.1
  • libX11 Linux Micro 6.0 1.8.7-159998.2.1
  • libX11 Linux Micro 6.0 1.8.7-159998.1.1
  • libX11 SLE Module for Basesystem 15 SP7 1.8.10-150700.4.8.1
  • libX11 SLES for SAP 15 SP5, SLES for SAP 15 SP4, SLES 15 SP5-LTSS +8 more 1.6.5-150000.3.41.1
  • libX11 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 1.8.10-160000.4.1
  • libX11 SLES for SAP 15 SP6, SLES 15 SP6-LTSS 1.8.7-150600.3.11.1
  • libX11 SLES LTSS Extended Security 12 SP5, SLES 12 SP5-LTSS 1.6.2-12.41.1

suse advisories SUSE-SU-2026:24552-1SUSE-SU-2026:24472-1SUSE-SU-2026:24365-1SUSE-SU-2026:4502-1SUSE-SU-2026:4501-1SUSE-SU-2026:4500-1

  • libX11 openSUSE Leap 16.0 1.8.10-160000.4.1
  • libX11 openSUSE Tumbleweed 1.8.13-2.1

opensuse advisories openSUSE-SU-2026:21908-1openSUSE-SU-2026:11833-1

  • libX11 AlmaLinux 9 1.8.12-1.el9_8.1
  • libX11-xcb AlmaLinux 9 1.8.12-1.el9_8.1
  • libX11-common AlmaLinux 9 1.8.12-1.el9_8.1
  • libX11 AlmaLinux 10 1.8.10-1.el10_2.1
  • libX11-xcb AlmaLinux 10 1.8.10-1.el10_2.1
  • libX11-common AlmaLinux 10 1.8.10-1.el10_2.1
  • libX11 AlmaLinux 8 1.6.8-10.el8_10
  • libX11-xcb AlmaLinux 8 1.6.8-10.el8_10

almalinux advisories ALSA-2026:91365ALSA-2026:91366ALSA-2026:89730

  • libX11 Rocky Linux 9 1.8.12-1.el9_8.1
  • libX11 Rocky Linux 10 1.8.10-1.el10_2.1
  • libX11 Rocky Linux 8 1.6.8-10.el8_10

rocky linux advisories RLSA-2026:98461RLSA-2026:91366RLSA-2026:91365RLSA-2026:89730

  • libx11 Alpine 3.24 1.8.14-r0

alpine advisories ALPINE-CVE-2026-88806

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • libX11 Azure Linux 3.0 1.8.14-1

azure linux advisories AZL-103388

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Is CVE-2026-88806 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-88806 updated cvss 7.5

libX11: libX11: Heap-based buffer overflow via malicious X server

  • Red Hat Enterprise Linux 6 libX11, libX11-common
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 7 libX11, libX11-common
    affected: workaround, no fix available
  • Red Hat Discovery 2 discovery/discovery-ui-rhel9 1793733716
    fixed: vendor fix RHSA-2026:94802
  • Red Hat Enterprise Linux AppStream (v. 8) libX11 1.6.8-10.el8_10, libX11-xcb 1.6.8-10.el8_10, libX11-common 1.6.8-10.el8_10
    fixed: vendor fix RHSA-2026:89730
  • Red Hat Enterprise Linux AppStream (v. 9) libX11 1.8.12-1.el9_8.1, libX11 1.8.12-1.el9_9.1, libX11-xcb 1.8.12-1.el9_8.1, libX11-xcb 1.8.12-1.el9_9.1, libX11-common 1.8.12-1.el9_8.1, libX11-common 1.8.12-1.el9_9.1
    fixed: vendor fix RHSA-2026:91365
  • Red Hat Enterprise Linux AppStream (v. 10) libX11 1.8.10-1.el10_2.1, libX11 1.8.13-1.el10_3.1, libX11-xcb 1.8.10-1.el10_2.1, libX11-xcb 1.8.13-1.el10_3.1, libX11-common 1.8.10-1.el10_2.1, libX11-common 1.8.13-1.el10_3.1
    fixed: vendor fix RHSA-2026:91366
  • Red Hat Enterprise Linux AppStream E4S (v.9.2) libX11 1.7.0-8.el9_2.1, libX11-xcb 1.7.0-8.el9_2.1, libX11-common 1.7.0-8.el9_2.1
    fixed: vendor fix RHSA-2026:95496
  • Red Hat Enterprise Linux AppStream E4S (v.9.4) libX11 1.7.0-9.el9_4.1, libX11-xcb 1.7.0-9.el9_4.1, libX11-common 1.7.0-9.el9_4.1
    fixed: vendor fix RHSA-2026:95497
show 4 more
  • Red Hat Enterprise Linux AppStream EUS (v. 10.0) libX11 1.8.10-1.el10_0.1, libX11-xcb 1.8.10-1.el10_0.1, libX11-common 1.8.10-1.el10_0.1
    fixed: vendor fix RHSA-2026:95499
  • Red Hat Enterprise Linux AppStream EUS (v.9.6) libX11 1.7.0-11.el9_6.1, libX11-xcb 1.7.0-11.el9_6.1, libX11-common 1.7.0-11.el9_6.1
    fixed: vendor fix RHSA-2026:95498
  • Red Hat Discovery 2 discovery/discovery-server-rhel9 1793734080
    not affected: vulnerable code not present
  • Red Hat Hardened Images libX11
    not affected: component not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
last mo.

Exploit prediction

0.20% chance of exploitation in the next 30 days, higher than 10% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

Affected products

  • x.org libX11

Classification

Weakness
  • CWE-122 Heap-based Buffer Overflow

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.