# CVE-2026-88806: libX11 XkbGetMap Reply Heap-based Buffer Overflow

> A malicious X server can trigger a heap-based buffer overflow in libX11, potentially allowing arbitrary code execution on the client system.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 21 Sep 2026
- **Updated:** 22 Sep 2026
- **Also known as:** ALPINE-CVE-2026-88806, ALSA-2026:89730, ALSA-2026:91365, ALSA-2026:91366, AZL-103388, BELL-CVE-2026-88806, CLSA-2026-1792810382, CLSA-2026-1792810818, DEBIAN-CVE-2026-88806, ECHO-4ee4-286e-3447, GHSA-xrgw-w7v2-3qp8, RLSA-2026:89730, ROOT-OS-DEBIAN-12-CVE-2026-88806, ROOT-OS-DEBIAN-13-CVE-2026-88806, SUSE-SU-2026:23885-1, SUSE-SU-2026:23899-1, UBUNTU-CVE-2026-88806, openSUSE-SU-2026:11833-1, openSUSE-SU-2026:21908-1

## What is CVE-2026-88806?

CVE-2026-88806 is a high-severity memory corruption vulnerability in x.org libX11, published on 21 Sep 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

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

Weakness: CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-88806?


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `libX11` | AlmaLinux:10 | All versions | 1.8.10-1.el10_2.1 |
| `libX11-common` | AlmaLinux:10 | All versions | 1.8.10-1.el10_2.1 |
| `libX11-devel` | AlmaLinux:10 | All versions | 1.8.10-1.el10_2.1 |
| `libX11-xcb` | AlmaLinux:10 | All versions | 1.8.10-1.el10_2.1 |
| `libX11` | AlmaLinux:8 | All versions | 1.6.8-10.el8_10 |
| `libX11-common` | AlmaLinux:8 | All versions | 1.6.8-10.el8_10 |
| `libX11-devel` | AlmaLinux:8 | All versions | 1.6.8-10.el8_10 |
| `libX11-xcb` | AlmaLinux:8 | All versions | 1.6.8-10.el8_10 |
| `libX11` | AlmaLinux:9 | All versions | 1.8.12-1.el9_8.1 |
| `libX11-common` | AlmaLinux:9 | All versions | 1.8.12-1.el9_8.1 |
| `libX11-devel` | AlmaLinux:9 | All versions | 1.8.12-1.el9_8.1 |
| `libX11-xcb` | AlmaLinux:9 | All versions | 1.8.12-1.el9_8.1 |
| `libX11` | Rocky Linux:8 | All versions | 0:1.6.8-10.el8_10 |
| `libX11` | SUSE:Linux Enterprise Server 16.0 | All versions | 1.8.10-160000.4.1 |
| `libX11` | SUSE:Linux Enterprise Server for SAP applications 16.0 | All versions | 1.8.10-160000.4.1 |
| `libX11` | SUSE:Linux Micro 6.2 | All versions | 1.8.10-160000.4.1 |
| `libX11` | openSUSE:Leap 16.0 | All versions | 1.8.10-160000.4.1 |
| `libX11` | openSUSE:Tumbleweed | All versions | 1.8.13-2.1 |

## How do I fix CVE-2026-88806?

Upgrade to a fixed version.

## Is CVE-2026-88806 being exploited?

There is no known exploitation of CVE-2026-88806 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-88806 and fix it if it is affected.

What it is: CVE-2026-88806 is a high-severity memory corruption vulnerability in x.org libX11, published on 21 Sep 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-88806 in the wild and no public exploit code.

Affected product: x.org libX11. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-88806/ (Markdown: https://insights.sbomify.com/CVE-2026-88806/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-88806
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-88806
- OSV: https://osv.dev/vulnerability/CVE-2026-88806

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-88806/
Summaries are generated and may contain mistakes; the official description above is the record.