# CVE-2026-109090: libXi heap overflow in DEVICE_ENABLE reply handling

Source: https://junglewise.ai/threats/cve-2026-109090-a-malicious-x-server-could-cause-a-heap-overflow-by-injecting-a  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-27. Updated: 2026-10-27  
License: CC BY 4.0 with a link back

CVE-2026-109090 · Severity: high · CVSS 7.5 · Published 2026-10-27

libXi is an X11 library that handles input device communication. A malicious X server can cause a heap buffer overflow by sending an oversized DEVICE_ENABLE reply, potentially allowing remote code execution or denial of service on systems using affected versions of the library.

Technologies: [X.Org libXi](https://junglewise.ai/threats/technologies/libxi). Vendors: [X.Org](https://junglewise.ai/threats/vendors/x-org).

## Quick answers

**Is CVE-2026-109090 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-109090 being exploited in the wild.

**How severe is CVE-2026-109090?** High severity, with a CVSS score of 7.5, published 27 October 2026.

**Which products and versions are affected?** X.Org libXi before 1.8.4.

**Is there a fix for CVE-2026-109090?** Yes: fixed in libXi 1.8.4. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-109090 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-109090?** Check whether you run X.Org libXi at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in libXi 1.8.4

## Technical details

The DEVICE_ENABLE message handler in libXi's XGetDeviceControl function allocates heap memory based on the wire-format message size (8 bytes) but then writes a full XDeviceEnableState structure, causing a heap overflow. The vulnerability requires a malicious or compromised X server and affects libXi versions before 1.8.4. A fix adds proper size validation to prevent writing beyond the allocated buffer.

## Affected products

- X.Org libXi before 1.8.4

## Timeline

- 2026-10-27: disclosed
- 2026-10-08: patched

## References

- [https://gitlab.freedesktop.org/xorg/lib/libxi/-/commit/4eb9f70b6](https://gitlab.freedesktop.org/xorg/lib/libxi/-/commit/4eb9f70b6)

## Related threats

- [libXi heap buffer overflow in DEVICE_RESOLUTION handling](https://junglewise.ai/threats/cve-2026-109089-a-buffer-overflow-when-handling-device-resolution-in-libxi)
- [libXi out-of-bounds read in XListInputDevices() class parsing](https://junglewise.ai/threats/cve-2026-94281-an-out-of-bounds-read-in-libxi-s-xlistinputdevices-class-parsing)
- [libXi out-of-bounds read in XI2 XIQueryDevice reply parsing](https://junglewise.ai/threats/cve-2026-93544-an-out-of-bounds-read-in-libxi-s-xi2-xiquerydevice-reply-parsing)
- [libXi out-of-bounds read in XI2 class parser](https://junglewise.ai/threats/cve-2026-93543-an-out-of-bounds-read-in-libxi-s-xi2-class-parser-in-libxi-before)
- [libXi out-of-bounds read in XI2 class parsing](https://junglewise.ai/threats/cve-2026-93542-an-out-of-bounds-read-in-libxi-s-xi2-class-parsing-via-size)