Hazard

Is CVE-2021-21017 being exploited?

Weaponised and widely attempted

Reliable public exploit code exists, or mass exploitation attempts are probable. Patch inside days, not weeks.

Adobe Acrobat and Reader Heap-based Buffer Overflow Vulnerability

Adobe · Acrobat and Reader

CVSS 8.8 EPSS 86% no public exploit indexed Fix deadline passed 17 November 2021

What it is

Acrobat Acrobat and Reader contain a heap-based buffer overflow vulnerability that could allow an unauthenticated attacker to achieve code execution in the context of the current user.

Why we say that

  • EPSS puts exploitation in the next 30 days at 86%
  • CISA's federal remediation deadline (2021-11-17) has passed
  • Listed in the CISA Known Exploited Vulnerabilities catalogue

Every line above comes from a named public source. Where the evidence is thin, we say so rather than inventing confidence — see methodology.

What to do

Apply updates per vendor instructions.

What it costs when this goes wrong

This is where UK enforcement meets the vulnerability record. Where an unfixed vulnerability leads to a breach, the ICO treats it as a security failure under UK GDPR. Recent cases:

All UK cases caused by unpatched software →