Threat Intelligence / CVE / CVE-2026-34621

CVE-2026-34621 — Adobe Acrobat DC (Continuous)

CISA KEV

CVSS v3.1 9.8 (CRITICAL) · EPSS 9.8% (higher than 93.0% of all scored CVEs) · Priority 9/10 · Published 2026-04-13

As of 2026-04-13, CVE-2026-34621 is a CRITICAL-severity vulnerability in Adobe Acrobat DC (Continuous), CVSS v3.1 9.8, EPSS 9.8% (93.0th percentile). It is listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-04-13), with a US federal remediation deadline of 2026-04-27. Threadlinqs Intelligence links 2 tracked threat campaigns to CVE-2026-34621, most recently “CVE-2026-34621: Adobe Acrobat and Reader Zero-Day Arbitrary Code Execution via Crafted PDF (Emergency Out-of-Band Patch)”.

Last updated: 2026-04-13

What is CVE-2026-34621?

Critical client-side remote code execution vulnerability in Adobe Acrobat and Acrobat Reader caused by a use-after-free condition in the JavaScript-to-AcroForm bridge of the PDF rendering engine. When an attacker-supplied PDF triggers a crafted sequence of form field mutations while a referenced object is being garbage collected, the engine dereferences a stale pointer controlled via heap grooming, yielding arbitrary code execution in the context of the process. Exploitation requires only that the victim open the malicious PDF with no further user interaction. Observed in-the-wild exploitation pivots out of Reader Protected Mode sandbox via a second-stage broker abuse chain. Post-exploitation drops a loader to %APPDATA%\Adobe\Reader\ establishing persistence via Scheduled Task 'AdobeAcroUpdater' and beacons to HTTPS C2 on port 443. Targeted phishing campaigns between 2026-04-02 and 2026-04-09 delivered weaponized PDFs as invoices and contract lures against finance, legal, and defense industrial base targets in North America and Europe. Adobe shipped emergency out-of-band patch APSB26-18 on 2026-04-13. CISA added to KEV catalog on 2026-04-13.

The record classifies CVE-2026-34621 under weakness classes CWE-416, CWE-787, CWE-1321. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs a user to take an action first, and has high impact on confidentiality, integrity, availability. 4 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 153 days ago.

Severity and exploitation probability

CVSS v3.1 base score: 9.8 — CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
EPSS (FIRST): 9.8% probability of exploitation in the next 30 days, higher than 93.0% of all scored CVEs
CISA KEV: Listed since 2026-04-13, federal remediation deadline 2026-04-27
Threadlinqs priority: 9/10 — CISA KEV-listed, which Threadlinqs floors at 9
Published: 2026-04-13

Is CVE-2026-34621 being exploited?

CISA added CVE-2026-34621 to the Known Exploited Vulnerabilities catalog on 2026-04-13, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2026-04-27 under BOD 22-01. It currently carries a trending score of 43 in the Threadlinqs vulnerability feed.

Affected products and versions

Adobe: Acrobat DC (Continuous), Acrobat Reader DC (Continuous), Acrobat 2020 (Classic), Acrobat Reader 2020 (Classic)

How to fix CVE-2026-34621

The record marks a vendor fix as available for CVE-2026-34621. Patch reference: https://helpx.adobe.com/security/products/acrobat/apsb26-18.html. Vendor advisory: https://helpx.adobe.com/security/products/acrobat/apsb26-18.html. Because CVE-2026-34621 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2026-04-27. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.

Threat activity tracking CVE-2026-34621

2 tracked threats in the Threadlinqs corpus reference CVE-2026-34621, either in the campaign’s CVE list or as an indicator on the campaign record.

CVE-2026-34621: Adobe Acrobat and Reader Zero-Day Arbitrary Code Execution via Crafted PDF (Emergency Out-of-Band Patch) — CRITICAL · 2026-04-13
CISA KEV Catalog Update: Seven Actively Exploited Vulnerabilities Added 2026-04-13 (Microsoft, Adobe, Fortinet) — CRITICAL · 2026-04-13

Sources

Seeded from threat-derived and not yet processed by the Threadlinqs enrichment pipeline, so blank CVSS, EPSS or KEV fields above mean NOT MEASURED rather than measured-absent.

Full detection coverage & IOCs for threats exploiting CVE-2026-34621 are available via the Threadlinqs MCP server (Purple tier). View plans →

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