# CVE-1999-0040: X Windowing System Xt library buffer overflow

Source: https://junglewise.ai/threats/cve-1999-0040-x-windowing-system-xt-library-buffer-overflow  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 1997-05-01. Updated: 2026-05-10  
License: CC BY 4.0 with a link back

CVE-1999-0040 · Severity: high · CVSS 7.2 · Published 1997-05-01

A security flaw in a core component of the X Windowing System, a graphical interface used on many Unix-like operating systems, could allow a local user to gain full administrative control. By exploiting a memory handling error in the Xt library, an individual with basic access to the system can execute commands with the highest level of privileges (root). This could lead to a complete compromise of the system, including unauthorized access to all data and the ability to modify or delete critical files.

Vendors: [X.Org Foundation](https://junglewise.ai/threats/vendors/x-org-foundation).

## Quick answers

**Is CVE-1999-0040 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-1999-0040 being exploited in the wild.

**How severe is CVE-1999-0040?** High severity, with a CVSS score of 7.2, published 1 May 1997.

**Which products and versions are affected?** X.Org Foundation Xt Library Versions prior to May 1997 patches.

**Is there a fix for CVE-1999-0040?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-1999-0040 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-1999-0040?** Check whether you run X.Org Foundation Xt Library 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.

## Technical details

A buffer overflow vulnerability exists in the X Toolkit Intrinsics (Xt) library, a foundational component of the X Windowing System. The flaw is triggered by improper bounds checking during the processing of specific inputs, such as environment variables or command-line arguments, by programs linked against the vulnerable library. A local attacker can exploit this by providing specially crafted input to a setuid-root application that utilizes the Xt library, leading to memory corruption and arbitrary code execution. Successful exploitation allows the attacker to bypass security controls and elevate their privileges to root. Patches were released by various Unix vendors following the initial disclosure in 1997.

## Affected products

- X.Org Foundation Xt Library (X Toolkit Intrinsics) Versions prior to May 1997 patches
- Sun Microsystems Solaris 2.3, 2.4, 2.5, 2.5.1

## Timeline

- 1997-05-01: disclosed: Initial publication of the vulnerability details.
- 1997-05-01: advisory: NVD published date.

## References

- [https://exchange.xforce.ibmcloud.com/vulnerabilities/CVE-1999-0040](https://exchange.xforce.ibmcloud.com/vulnerabilities/CVE-1999-0040)