Threats / Adobe / CVE-2021-21017
CVE-2021-21017
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Adobe Acrobat and Reader vulnerability
Adobe Acrobat and Reader contain a heap-based buffer overflow vulnerability allowing unauthenticated attackers to execute code in the current user's context.
Verdict
Today item — known-exploited.
A heap buffer overflow in Adobe's PDF readers enables remote code execution without authentication. The high EPSS score and active exploitation in the wild indicate immediate risk to users opening untrusted documents.
01
Is it exploitable?
— the evidence, ranked above the scoreExploit available
Public proof-of-concept exploit code is cataloged for this vulnerability.We link the existence of the exploit; we do not host or redistribute payloads.
Reported exploitation
2 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03).
Probability (EPSS)
EPSS 0.86274 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Adobe, Acrobat and Reader. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-122 Heap-based Buffer Overflow — weakness family: Memory safety.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft a malicious PDF document that triggers a heap buffer overflow when parsed by the target's Acrobat or Reader application.
Business
Users cannot safely open PDF files from untrusted sources, disrupting document workflows and creating liability for organizations distributing or receiving files.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I deliver the malicious PDF via email, web download, or file sharing to reach potential victims.
Business
Email security and content filtering systems must be updated to detect exploit patterns, increasing operational overhead and security costs.
3
Lateral reach — past segmentation narrative 3
Attacker
When the victim opens the PDF, the buffer overflow executes arbitrary code with the privileges of the logged-in user.
Business
Compromised user accounts lead to lateral movement, data exfiltration, and potential system-wide compromise depending on user privileges.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05