Threats / Adobe / CVE-2021-28550
CVE-2021-28550
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-08-04
Adobe Acrobat and Reader vulnerability
Adobe Acrobat and Reader use-after-free vulnerability allows unauthenticated attackers to execute arbitrary code with user privileges.
Verdict
Today item — known-exploited.
A use-after-free flaw in Adobe Acrobat and Reader enables remote code execution without authentication. The vulnerability has been observed in active exploitation. CVSS assessment pending; EPSS indicates moderate predicted probability of exploitation.
CISA KEV Yes · 2021-11-035EPSS 0.52005 (verify live)6CVSS 9.63CISA SSVC Exploitation: active · Automatable: no · Impact: total4
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
4 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 0.52005 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 9.6 (CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H) · Affected: Adobe, Acrobat and Reader. Confirm exact fixed builds in the vendor advisory.CVSS — CNA-assigned (CVE.org), version 3.0, set at disclosure.
Weakness (CWE)
Mapped to CWE-416 Use After Free — weakness family: Memory safety.CWE — CNA-assigned (CVE.org); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: no · Technical Impact: totalCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog 62 days after the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
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 or exploit delivery mechanism targeting the use-after-free condition in memory management.
Business
Users opening untrusted documents face arbitrary code execution within their application context, risking data theft and system compromise.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I deliver the exploit through email, web download, or document-sharing platforms where Acrobat or Reader processes files automatically.
Business
Attack surface expands across email gateways and web properties; endpoint detection becomes critical to prevent lateral movement.
3
Lateral reach — past segmentation narrative 3
Attacker
I execute malware, steal credentials, or establish persistence on the compromised system under the current user's privileges.
Business
Organizational data confidentiality and integrity are compromised; incident response and forensics costs escalate with widespread infection.
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