---
title: "CVE-2026-88806: libX11 - Buffer Overflow"
description: "libX11 < 1.8.14 contains a buffer overflow caused by improper handling of XkbGetMap overflowing the key_sym_map, letting a malicious X server execute arbitrary code, exploit requires a malicious X server."
url: https://panop.io/threat-heartbeat/CVE-2026-88806/
---

# CVE-2026-88806 libX11 - Buffer Overflow

libX11 < 1.8.14 contains a buffer overflow caused by improper handling of XkbGetMap overflowing the key\_sym\_map, letting a malicious X server execute arbitrary code, exploit requires a malicious X server.

CVSS base score 7.5 /10

High

CISA KEV

Not listed

Public exploit

None known

EPSS

0.20% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-88806)

## Details

Type

Buffer Overflow

Impact

Remote Code Execution

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

Published

21 September 2026

Updated

15 October 2026

Weakness

[CWE-122](https://cwe.mitre.org/data/definitions/122.html)

## Vendor fix

Update to version 1.8.14 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-88806](https://nvd.nist.gov/vuln/detail/CVE-2026-88806)
- [https://gitlab.freedesktop.org/xorg/lib/libx11/-/merge\_requests/309](https://gitlab.freedesktop.org/xorg/lib/libx11/-/merge_requests/309)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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