ZDI-26-870: (0Day) Ashlar-Vellum Cobalt XE File Parsing Stack-based Buffer Overflow Remote Code Execution Vulnerability
Source Zero Day Initiative
Not known to be exploited.
Data as of 4 Nov 2026, 14:44 UTC
Rated High by Zero Day Initiative · CVSS not yet scored by NVD
Exploitation evidence
Disclosed: evidence found.
Public on cve.org; its publication date is not in this record
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 4 Nov 2026.
What to do
AI-suggested
Until a fix is available, users should avoid opening files or visiting pages from untrusted sources to prevent exploitation.
Description
A stack-based buffer overflow vulnerability in Ashlar-Vellum Cobalt XE file parsing allows remote attackers to execute arbitrary code. Exploitation requires user interaction, such as opening a malicious file or visiting a malicious page. The vulnerability is assigned CVE-2026-121744 with a high severity rating by ZDI.