# CVE-2026-109089: libXi heap buffer overflow in DEVICE_RESOLUTION handling

Source: https://junglewise.ai/threats/cve-2026-109089-a-buffer-overflow-when-handling-device-resolution-in-libxi  
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-2026-109089 · Severity: high · CVSS 7.5 · Published 2026-10-27

libXi is a library that applications use to communicate with X servers for input device handling. A malicious X server can trigger a heap buffer overflow in libXi's DEVICE_RESOLUTION handler, potentially allowing an attacker to execute code or crash any application using the library. This vulnerability requires interaction with a compromised or attacker-controlled X server.

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

## Quick answers

**Is CVE-2026-109089 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-109089 being exploited in the wild.

**How severe is CVE-2026-109089?** 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-2026-109089?** 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-2026-109089 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-109089?** 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

A heap buffer overflow occurs in libXi's XGetDeviceControl function when processing DEVICE_RESOLUTION control responses from an X server. The vulnerability arises because the size and fill operations use different values to key off the control type, allowing a hostile server to respond with a DEVICE_RESOLUTION control that has a small fixed-size but still trigger an unbounded valuator copy. The fix requires validation that the reply control type matches the request type before performing the copy operation.

## Affected products

- X.Org libXi before 1.8.4

## Timeline

- 2026-10-27: disclosed
- 2026-10-01: patched

## References

- [https://gitlab.freedesktop.org/xorg/lib/libxi/-/commit/f7836d0a0](https://gitlab.freedesktop.org/xorg/lib/libxi/-/commit/f7836d0a0)

## Related threats

- [libXi heap overflow in DEVICE_ENABLE reply handling](https://junglewise.ai/threats/cve-2026-109090-a-malicious-x-server-could-cause-a-heap-overflow-by-injecting-a)
- [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)