CVE-2025-7997: Ashlar Cobalt XE File Parsing RCE Flaw

CVE-2025-7997 Overview

CVE-2025-7997 is an out-of-bounds read vulnerability [CWE-125] in Ashlar-Vellum Cobalt that enables arbitrary code execution. The flaw resides in the parser for XE files and stems from insufficient validation of user-supplied data. An attacker can craft a malicious XE file that triggers a read before the start of an allocated data structure. Successful exploitation runs code in the context of the current Cobalt process. Exploitation requires user interaction: the victim must open a malicious file or visit a malicious page that delivers one. The Zero Day Initiative tracked this issue as ZDI-CAN-26045 and published advisory ZDI-25-719.

Critical Impact
A crafted XE file opened in Ashlar-Vellum Cobalt allows arbitrary code execution with the privileges of the user running the application.

Affected Products

Ashlar-Vellum Cobalt (per CPE cpe:2.3:a:ashlar:cobalt:-:*:*:*:*:*:*:*)
Component: ashlar:cobalt
Vendor: Ashlar-Vellum

Discovery Timeline

2025-09-17 - CVE-2025-7997 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-7997

Vulnerability Analysis

The vulnerability is an out-of-bounds read [CWE-125] within Ashlar-Vellum Cobalt's XE file parser. When the application processes a crafted XE file, the parser dereferences a pointer that resolves to memory located before the start of an allocated buffer. This out-of-bounds access leaks or misinterprets adjacent process memory and corrupts control flow data used during subsequent parsing operations. Attackers can shape the file contents to influence the read offset, the data returned, and the downstream logic that consumes that data. The end result is arbitrary code execution inside the Cobalt process. The Zero Day Initiative publication notes that the flaw is exploitable when a user opens a malicious file or visits a page that delivers one through a registered file handler.

Root Cause

The parser fails to validate user-controlled fields in the XE file before using them to compute a memory offset or index. Because the computed location can fall before the start of an allocated structure, the read accesses memory outside the intended object. Missing bounds enforcement on attacker-controlled length and offset values is the direct cause.

Attack Vector

Exploitation is local and requires user interaction. An attacker delivers a malicious XE file by email, download link, or web page. When the user opens the file in Cobalt, the parser processes the malicious structure and the out-of-bounds read triggers. The attacker gains code execution at the privilege level of the current user. See the Zero Day Initiative Advisory ZDI-25-719 for the upstream technical write-up.

Detection Methods for CVE-2025-7997

Indicators of Compromise

Unexpected .xe files arriving via email attachments, downloads, or removable media followed by Cobalt process launches.
Cobalt process crashes, access violations, or abnormal child process creation shortly after opening an XE file.
Outbound network connections initiated by the Cobalt process to untrusted destinations after document open events.

Detection Strategies

Monitor process creation events where Cobalt spawns shells, scripting engines, or LOLBins such as cmd.exe, powershell.exe, or rundll32.exe.
Inspect file write and load events for XE files originating from internet zone locations (Downloads, Temp, browser cache).
Hunt for image loads of unsigned or unusual modules inside the Cobalt process address space.

Monitoring Recommendations

Forward endpoint telemetry covering process, file, and module-load events from workstations running Ashlar-Vellum Cobalt to a central analytics platform.
Alert on Cobalt crash dumps and Windows Error Reporting events that correlate with XE file opens.
Track email gateway and web proxy logs for inbound XE file transfers and review delivery to engineering or design teams.

How to Mitigate CVE-2025-7997

Immediate Actions Required

Restrict opening of XE files to trusted, verified sources only and treat unsolicited XE attachments as suspicious.
Remove or disable file association handlers that auto-launch Cobalt from browsers or email clients.
Run Cobalt under a standard user account rather than an administrative account to limit the blast radius of code execution.

Patch Information

Consult Ashlar-Vellum for an updated version of Cobalt that addresses CVE-2025-7997. No vendor advisory URL was published in the NVD record at the time of writing. Refer to the Zero Day Initiative Advisory ZDI-25-719 for upstream coordination status and any vendor fix references.

Workarounds

Block delivery of .xe files at email and web gateways for users who do not require them.
Open untrusted XE files only inside an isolated virtual machine or sandbox without network access.
Apply application allowlisting to prevent Cobalt from launching child processes such as scripting interpreters or shells.

bash

# Example: block .xe attachments at a mail transport layer (illustrative)
# Adjust to your gateway's syntax (e.g., Exchange transport rule, Postfix header_checks)
/name=.*\.xe$/  REJECT XE files are blocked by policy (CVE-2025-7997)