Quick answers
- Is CVE-2026-78521 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-78521 being exploited in the wild.
- How severe is CVE-2026-78521?
- High severity, with a CVSS score of 8.8, published 8 September 2026.
- Which products and versions are affected?
- Microsoft Office Word.
- Is there a fix for CVE-2026-78521?
- 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-2026-78521 attacked?
- It is attacked over the network.
- Am I affected by CVE-2026-78521?
- Check whether you run Microsoft Office Word. 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 heap-based buffer overflow exists in Microsoft Office Word that can be triggered by a specially crafted document. The vulnerability is reachable over the network without requiring user authentication to the affected system, though user interaction (opening a malicious document) is typically required. An attacker can exploit this flaw to achieve remote code execution with the privileges of the user running Word. The vulnerability has a CVSS score of 8.8, indicating high severity, though no active exploitation in the wild has been reported as of the publication date.
Affected products
- Microsoft Office Word
Timeline
- 2026-09-08: disclosed