Adobe Reader Zero-Day Exploited via Malicious PDFs Since December 2025
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2026-34621 | Actively Exploited Prototype Pollution RCE in Adobe Acrobat and Reader Adobe Acrobat and Acrobat Reader are affected by a prototype pollution vulnerability (CWE-1321) in which improperly controlled modification of object prototype attributes can lead to arbitrary code execution in the context of the current user. Attackers trigger the flaw by convincing a victim to open a malicious file, typically a crafted PDF, so user interaction is required. Successful exploitation yields code execution as the victim, with the CVSS scope-changed metric indicating impact that extends beyond the vulnerable component. Anyone running Acrobat or Reader versions 24.001.30356 or earlier or 26.001.21367 or earlier is affected. The flaw is being actively exploited in the wild — reportedly via malicious PDFs since December 2025 as a zero-day — and CISA added it to the Known Exploited Vulnerabilities catalog on 2026-04-13 after fixes shipped in Adobe's April 2026 Patch Tuesday release; EPSS assigns a 7.1% probability of exploitation within 30 days (94th percentile). Do: Upgrade Acrobat and Reader to a version later than 24.001.30356 (24.001 series) or 26.001.21367 (26.001 series) via Adobe's April 2026 security update, and audit installed versions across all endpoints. As a CISA KEV entry, US federal agencies must apply the vendor mitigations per BOD 22-01 guidance or discontinue use of the product if mitigations are unavailable. Until patched, treat PDFs from untrusted sources with caution and monitor for suspicious child-process activity spawned by Acrobat/Reader when files are opened. | 8.6 | 7% | KEV |
| masshundreds of millions of Acrobat/Reader installations worldwide, with likely millions still unpatched |
Full article380 words · extracted from thehackernews.com · click to collapse
Ravie LakshmananApr 09, 2026Vulnerability / Threat Intelligence
Threat actors have been exploiting a previously unknown zero-day vulnerability in Adobe Reader using maliciously crafted PDF documents since at least December 2025.
The finding, detailed by EXPMON's Haifei Li, has been described as a highly-sophisticated PDF exploit. The artifact ("Invoice540.pdf") first appeared on the VirusTotal platform on November 28, 2025. A second sample was uploaded to VirusTotal on March 23, 2026.
Given the name of the PDF document, it's likely that there is an element of social engineering involved, with the attackers luring unsuspecting users into opening the files on Adobe Reader. Once launched, it automatically triggers the execution of obfuscated JavaScript to harvest sensitive data and receive additional payloads.
Security researcher Gi7w0rm, in an X post, said the PDF documents observed contain Russian language lures and refer to issues regarding current events related to the oil and gas industry in Russia.
"The sample acts as an initial exploit with the capability to collect and leak various types of information, potentially followed by remote code execution (RCE) and sandbox escape (SBX) exploits," Li said.
"It abuses zero-day/unpatched vulnerability in Adobe Reader that allows it to execute privileged Acrobat APIs, and it is confirmed to work on the latest version of Adobe Reader."
It also comes with capabilities to exfiltrate the collected information to a remote server ("169.40.2[.]68:45191") and receive additional JavaScript code to be executed.
This mechanism, Li argued, could be used to collect local data, perform advanced fingerprinting attacks, and set the stage for follow-on activity, including delivering additional exploits to achieve code execution or sandbox.
The exact nature of this next-stage exploit remains unknown as no response was received from the server. This, in turn, could imply the local testing environment from which the request was issued did not meet the necessary criteria to receive the payload.
"Nevertheless, this zero-day/unpatched capability for broad information harvesting and the potential for subsequent RCE/SBX exploitation is enough for the security community to remain on high alert," Li said.
Update
Adobe has released security updates for the vulnerability (CVE-2026-34621, CVSS score: 9.6). Please check here for more details.
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Text extracted automatically; images, tables and formatting may be missing. Original: https://thehackernews.com/2026/04/adobe-reader-zero-day-exploited-via.html