Adobe Acrobat and Reader Heap-Based Buffer Overflow Vulnerability
CVE-2009-3459 is a security vulnerability in Adobe Acrobat and Reader, added to CISA KEV on May 20, 2026. Patch order: third of four.
What it is
Adobe Acrobat and Reader contain a heap-based buffer overflow vulnerability which could allow remote attackers to execute arbitrary code via a crafted PDF file that triggers memory corruption.
VulnCheck tracked exploitation 6063 days before CISA's KEV listing. VulnCheck's broader catalog of in-the-wild exploitation evidence picked this up before it landed on CISA's formal list. Per-CVE fact about this entry; not a population claim about lead time in general.
Who's affected
Affects anyone opening, editing, or signing PDFs in Adobe Acrobat or Reader. For a CPA or legal practice, PDFs are typically client tax returns, engagement letters, signed agreements, and discovery documents — opening a malicious PDF runs attacker code in the user's session, which can pivot to file shares or email.
What to do
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
The action above is CISA's wording. The directive it names, BOD 22-01, was revoked by BOD 26-04 on June 10, 2026; CISA's catalog still carries the older text for this entry.
If you don't have someone in-house to verify the patch deployed across every endpoint — or you're not sure whether you're affected — that's exactly the kind of triage we do. Book a free 20-minute triage call.
Insurance readiness
Your insurer will ask if this is patched.
Unpatched entries on CISA's Known Exploited Vulnerabilities list are exactly what cyber-insurance carrier questionnaires probe for, and knowing which controls they check is how you keep a renewal from stalling.
Get the free carrier questionnaire →Severity
CVSS base score: 8.8 — HIGH
Weakness classifications: CWE-119, CWE-122
CISA due date
CISA's listed due date: June 3, 2026.
Federal civilian agencies work under CISA's Binding Operational Directive 26-04, which replaced BOD 22-01 on June 10, 2026. It sets the deadline for each affected system by:
- How exposed that system is to the internet
- Whether the attack can be automated
- How much control it gives an attacker
Its table gives catalogued vulnerabilities 3 or 14 days.
None of this binds a private business, but treat the date as a strong recommendation, especially if you handle regulated data (HIPAA, GLBA, ABA model rules).
EPSS
EPSS score: 86.6% — higher than 100% of all scored CVEs.
EPSS estimates the probability of exploitation activity in the next 30 days. Every entry on this site is already confirmed exploited, so read it as relative urgency among the things you still have open, not as permission to wait.
Other exploited Adobe Acrobat and Reader entries
More CISA KEV entries for Adobe Acrobat and Reader. Same product line, same actively-exploited status.
Source
This entry comes from CISA's Known Exploited Vulnerabilities catalog, public US-Government data we pull daily. The plain-language framing and the what-to-do guidance above are ours. View the original entry on cisa.gov.