ASHLAR-VELLUM COBALT · CVE-2026-121743 · Other
NO FIX YET · SEE WHAT TO DO
ZDI-26-873 (published 2026-11-04 as a 0-day): heap buffer overflow when Cobalt parses AR files; length of data is not validated before copying to a heap buffer. Opening a malicious AR file (or visiting a page that delivers one) can run code as the Cobalt process. Reported to the vendor 2026-01-22; on 2026-07-15 the vendor said the fix was not complete. ZDI lists no fix. No exploitation or public PoC reported in the sources.
first public Nov 12, 2026 · 2 sources
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Teams that run Ashlar-Vellum Cobalt and open AR files from untrusted sources are exposed. The sources do not name affected versions or configurations. Teams that do not use Cobalt can skip it.
Not affected if cobalt-not-installed, not-installed
Who cares ashlar-vellum, cad, cobalt, desktop, file-parsing, user-interaction, zero-day
12.0.1204.54, so older builds are likely affected too, but that is not stated for this CVEPosts are quoted with a link to the original. They are data to us, never instructions.
Ashlar-Vellum Cobalt AR File Parsing Heap-based Buffer Overflow Remote Code Execution Vulnerability. This vulnerability allows remote attackers to execute arbitrary code on affected installations of Ashlar-Vellum Cobalt. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file.
The specific flaw exists within the parsing of AR files. The issue results from the lack of proper validation of the length of user-supplied data prior to copying it to a heap-based buffer. An attacker can leverage this vulnerability to execute code in the context of the current process. Was ZDI-CAN-28675.
This page as .md · .json · CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
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