CVE-2026-34621: in the CISA KEV catalogue

Adobe Acrobat and Reader Prototype Pollution Vulnerability. CISA added CVE-2026-34621 to the Known Exploited Vulnerabilities catalogue on 2026-04-13 with a default due date of 2026-04-27. Known ransomware campaign use: Unknown. Forensic triage flag: No.

Adobe Acrobat and Reader contain a prototype pollution vulnerability that allows for arbitrary code execution. (CISA description)

Vendor / product: Adobe Acrobat and Reader
CWE: CWE-1321
CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
EPSS: 7.2%, percentile 94 (scored 2026-11-04)

EPSS puts about 7.2 in 100 odds (7.2%) on exploitation activity being observed in the next 30 days. Its score is higher than or equal to that of 94% of scored CVEs. This is a model estimate about exploitation anywhere, not about your environment.

Vendor and reference links (from CISA)

Your own deadline under CISA BOD 26-04 depends on exposure, automatability and technical impact: work it out with the BOD 26-04 calculator.

Data dates. CISA KEV catalogue version 2026.11.04, released 2026-11-04, 1,768 entries (checked 2026-11-05). EPSS model v2026.06.15, scored 2026-11-04, 400,189 CVEs. Sources: CISA and FIRST (EPSS by FIRST; scores generated by Empirical Security). Copied to our own database and refreshed automatically; if a refresh fails, the previous copy keeps serving with its own date.

Frequently asked questions

Is CVE-2026-34621 in the CISA KEV catalogue?

Yes. CISA added CVE-2026-34621 (Adobe Acrobat and Reader Prototype Pollution Vulnerability) to the Known Exploited Vulnerabilities catalogue on 2026-04-13. CISA's default due date for it is 2026-04-27.

Is CVE-2026-34621 used in ransomware attacks?

CISA marks known ransomware campaign use as Unknown for CVE-2026-34621. That means CISA lacks confirmation, not that ransomware groups do not use it.

What should I do about CVE-2026-34621?

CISA's required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Sources

CISA, Known Exploited Vulnerabilities Catalog (accessed 2026-11-03)
FIRST, Exploit Prediction Scoring System (EPSS) (EPSS by FIRST; scores generated by Empirical Security)
NVD record for CVE-2026-34621