Malicious PDF reveals active Adobe Reader zero-day in the wild


Malicious PDF reveals active Adobe Reader zero-day in the wild

Pierluigi Paganini
April 09, 2026

Hackers used an Adobe Reader zero-day for months. Researcher Haifei Li found a malicious PDF and asks the community to help analyze it.

Hackers used an Adobe Reader zero-day for months to deliver a sophisticated PDF exploit. Cybersecurity researcher Haifei Li, founder of Expmon, discovered the malicious file and warned the community.

On March 26, a suspicious PDF was submitted to EXPMON and flagged by its advanced “detection in depth” feature, despite low antivirus detection (13/64 on VirusTotal).

Adobe Reader

The system marked it for manual review, highlighting potential hidden threats. EXPMON identifies exploits through automated alerts, analyst inspection of logs and indicators, and large-scale data analysis. This case shows how advanced detection can uncover sophisticated zero-day activity that traditional tools may miss, though it requires expert analysis to confirm.

He is now asking security experts to help analyze the exploit, understand how it works, and determine its impact, as the vulnerability appears unpatched and actively abused in real-world attacks.

A researcher who goes online with the moniker Gi7w0rm reported that documents employed in the campaign contain Russian language lures and refer to issues regarding current events related to the oil and gas industry in Russia.

The sample analyzed by the Li works as an initial exploit that abuses an unpatched Adobe Reader flaw to run privileged APIs on fully updated systems.

It uses “util.readFileIntoStream()” to read local files and collect sensitive data. Then it calls “RSS.addFeed()” to send stolen data to a remote server and receive more malicious JavaScript.

“Based on our analysis, 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. 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.” reads the report published by Haifei Li. “Specifically, it calls the “util.readFileIntoStream()” API, allowing it to read arbitrary files (accessible by the sandboxed Reader process) on the local system. In this way, it can collect a wide range of information from the local system and steal local file data.”

This lets attackers profile victims, steal information, and decide whether to launch further attacks, including remote code execution or sandbox escape if the target meets specific conditions.

During the tests, researchers connected to the server but received no response or additional exploit. The attacker likely requires specific target conditions that the test setup did not meet.

“However, during our tests, we were unable to obtain the said additional exploit – the server was connected but no response.” continues the report. “This could be due to various reasons – for example, our local testing environments may not have met the attacker’s specific criteria.”

On April 8, 2025, researcher @greglesnewich found a new variant that connects to the IP address 188.214.34.20:34123. This sample appeared was uploaded on VirusTotal on November 28, 2025, a circumstance that suggests the hacking campaign has been ongoing for at least four months.

The researcher N3mes1s published a full forensic analysis of the Adobe Reader Zero-Day PDF exploit.

Follow me on Twitter: @securityaffairs and Facebook and Mastodon

Pierluigi Paganini

(SecurityAffairs – hacking, Adobe Reader)







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Do you ever walk past a person on the streets exhibiting mental health issues and wonder what happened to their family? I have a brother—or at least, I used to. I worry about where he is and hope he is safe. He hasn’t taken my call since 2014.

James and his brother as young children playing together before his brother became sick. James is on the right and his brother is on the left.

James and his brother as young children playing together before his brother became sick. James is on the right and his brother is on the left.

When I was 13, I had a very bad day. I was in the back of the car, and what I remember most was the world-crushing sound violently panging off every surface: he was pounding his fists into the steering wheel, and I worried it would break apart. He was screaming at me and my mother, and I remember the web of saliva and tears hanging over his mouth. His eyes were red, and I knew this day would change everything between us. My brother was sick.

Nearly 20 years later, I still have trouble thinking about him. By the time we realized he was mentally ill, he was no longer a minor. The police brought him to a facility for the standard 72-hour hold, where he was diagnosed with paranoid delusional schizophrenia. Concluding he was not a danger to himself or others, they released him.

There was only one problem: at 18, my brother told the facility he was not related to us and that we were imposters. When they let him out, he refused to come home.

My parents sought help and even arranged for medication, but he didn’t take it. Before long, he disappeared.

My brother’s decline and disappearance had nothing to do with the common narratives about drug use or criminal behavior. He was sick. By the time my family discovered his condition, he was already 18 and legally independent from our custody.

The last time he let me visit, I asked about his bed. I remember seeing his dirty mattress on the floor beside broken glass and garbage. I also asked about the laptop my parents had gifted him just a year earlier. He needed the money, he said—and he had maxed out my parents’ credit card.

In secret from my parents, I gave him all the cash I had saved. I just wanted him to be alright.

My parents and I tried texting and calling him; there was no response except the occasional text every few weeks. But weeks turned into months.

Before long, I was graduating from high school. I begged him to come. When I looked in the bleachers, he was nowhere to be seen. I couldn’t help but wonder what I had done wrong.

The last time I heard from him was over the phone in 2014. I tried to tell him about our parents and how much we all missed him. I asked him to be my brother again, but he cut me off, saying he was never my brother. After a pause, he admitted we could be friends. Making the toughest call of my life, I told him he was my brother—and if he ever remembers that, I’ll be there, ready for him to come back.

I’m now 32 years old. I often wonder how different our lives would have been if he had been diagnosed as a minor and received appropriate care. The laws in place do not help families in my situation.

My brother has no social media, and we suspect he traded his phone several years ago. My family has hired private investigators over the years, who have also worked with local police to try to track him down.

One private investigator’s report indicated an artist befriended my brother many years ago. When my mother tried contacting the artist, they said whatever happened between them was best left in the past and declined to respond. My mom had wanted to wish my brother a happy 30th birthday.

My brother grew up in a safe, middle-class home with two parents. He had no history of drug use or criminal record. He loved collecting vintage basketball cards, eating mint chocolate chip ice cream, and listening to Motown music. To my parents, there was no smoking gun indicating he needed help before it was too late.

The next time you think about a person screaming outside on the street, picture their families. We need policies and services that allow families to locate and support their loved ones living with mental illness, and stronger protections to ensure that individuals leaving facilities can transition into stable care. Current laws, including age-based consent rules, the limits of 72-hour holds, and the lack of step-down or supported housing options, leave too many families without resources when a serious diagnosis occurs.

Governments and lawmakers need to do better for people like my brother. As someone who thinks about him every day, I can tell you the burden is too heavy to carry alone.

James Finney-Conlon is a concerned brother and mental health advocate. He can be reached at [email protected].



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