# CVE-2026-121753: Ashlar-Vellum Cobalt XE file parsing use-after-free remote code execution

Source: https://junglewise.ai/threats/cve-2026-121753-ashlar-vellum-cobalt-xe-file-parsing-use-after-free-remote-code  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-12. Updated: 2026-11-12  
License: CC BY 4.0 with a link back

CVE-2026-121753 · Severity: high · CVSS 7.8 · Published 2026-11-12

Ashlar-Vellum Cobalt is a design and engineering application used for creating technical drawings and models. This vulnerability allows attackers to execute arbitrary code by crafting a malicious XE file that, when opened by a user, triggers a use-after-free memory error. An attacker could gain complete control over the affected system to steal data, install malware, or disrupt operations.

Technologies: [Ashlar-Vellum Cobalt](https://junglewise.ai/threats/technologies/ashlar-vellum-cobalt). Vendors: [Ashlar-Vellum](https://junglewise.ai/threats/vendors/ashlar-vellum).

## Quick answers

**Is CVE-2026-121753 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-121753 being exploited in the wild.

**How severe is CVE-2026-121753?** High severity, with a CVSS score of 7.8, published 12 November 2026.

**Which products and versions are affected?** Ashlar-Vellum Cobalt.

**Is there a fix for CVE-2026-121753?** No fixed version is recorded yet. Restrict user interaction with XE files from untrusted sources; avoid opening XE files from suspicious or unknown origins until a patch is available. 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-2026-121753 attacked?** It is attacked with local access.

**Am I affected by CVE-2026-121753?** Check whether you run Ashlar-Vellum Cobalt. 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


Restrict user interaction with XE files from untrusted sources; avoid opening XE files from suspicious or unknown origins until a patch is available.

## Technical details

A use-after-free vulnerability exists in Cobalt's XE file parser due to insufficient validation of object existence before dereferencing. An attacker can craft a malicious XE file that causes the application to operate on a freed object, leading to arbitrary code execution in the process context. User interaction is required (opening a malicious file or visiting a malicious page), and no fix has been disclosed.

## Affected products

- Ashlar-Vellum Cobalt

## Timeline

- 2025-12-16: disclosed: Vulnerability reported to vendor
- 2026-11-04: advisory: Coordinated public disclosure

## References

- [https://www.zerodayinitiative.com/advisories/ZDI-26-872/](https://www.zerodayinitiative.com/advisories/ZDI-26-872/)

## Related threats

- [Ashlar-Vellum Cobalt heap buffer overflow in LI file parsing](https://junglewise.ai/threats/cve-2026-121752-ashlar-vellum-cobalt-li-file-parsing-heap-based-buffer-overflow)
- [Ashlar-Vellum Cobalt stack-based buffer overflow in XE file parsing](https://junglewise.ai/threats/cve-2026-121744-ashlar-vellum-cobalt-xe-file-parsing-stack-based-buffer-overflow)
- [Ashlar-Vellum Cobalt heap-based buffer overflow in AR file parsing](https://junglewise.ai/threats/cve-2026-121743-ashlar-vellum-cobalt-ar-file-parsing-heap-based-buffer-overflow)
- [Ashlar-Vellum Cobalt use-after-free in XE file parsing](https://junglewise.ai/threats/cve-2026-121742-ashlar-vellum-cobalt-xe-file-parsing-use-after-free-remote-code)