CVE-2018-4878

CVE-2018-4878: Adobe Flash Player Use-After-Free Arbitrary Code Execution Vulnerability

AI-generated analysis based on the vulnerability data on this page.

Summary

A use-after-free vulnerability in Adobe Flash Player before version 28.0.0.161 allows attackers to execute arbitrary code. The flaw resides in the Primetime SDK, where a dangling pointer related to media player listener object handling can be leveraged for memory corruption. This vulnerability was actively exploited in the wild during January and February 2018.

Background

Adobe Flash Player was a widely deployed browser plugin and runtime for multimedia and rich Internet applications. Despite gradual deprecation, it remained a high-value target for attackers due to its ubiquity and complex codebase. In early 2018, security researchers identified in-the-wild exploitation of a zero-day vulnerability in Flash Player, later assigned CVE-2018-4878. The vulnerability was leveraged by threat actors in targeted attacks and mass malspam campaigns.

Root Cause

CWE-416: Use-After-Free

The vulnerability stems from a dangling pointer in the Adobe Flash Player Primetime SDK. Specifically, when the media player handles listener objects, a pointer to an object may remain accessible after the object has been freed. An attacker who can trigger this condition can corrupt memory and gain control of execution flow. The use-after-free occurs because the application fails to properly invalidate or clear references to freed memory during listener object lifecycle transitions.

Impact

The CVSS v2 base score of 7.5 reflects a network-accessible, low-complexity attack requiring no authentication, yielding partial impacts across confidentiality, integrity, and availability. The CVSS v3 score of 7.8 (HIGH) accounts for local attack vector (via user execution), but emphasizes the severe consequences: high confidentiality, integrity, and availability impacts. Successful exploitation leads to arbitrary code execution in the context of the Flash Player process, which typically runs with the privileges of the logged-in user.

Exploitation Walkthrough

Ethics Note: This section describes the attack from a defensive and forensic perspective. No weaponized exploit code or step-by-step reproduction instructions are provided.

Threat actors typically delivered exploitation via malicious Microsoft Office documents with embedded Adobe Flash content. When a victim opened the document, the embedded Flash object loaded and triggered the use-after-free condition in the Primetime SDK listener handling. Memory corruption was then leveraged to achieve arbitrary code execution within the Flash process. In observed campaigns, this initial access was used to download and execute secondary payloads.

Defensive analysts should look for:

• Office documents containing unexpected or obfuscated embedded Flash objects.
• Process memory anomalies in Flash Player or browser plugin containers.
• Network connections initiated by Office applications or Flash processes to suspicious domains.

Affected and Patched Versions

Affected:

• Adobe Flash Player versions prior to 28.0.0.161
• Adobe Flash Player for Edge, Internet Explorer 11, and Chrome (bundled versions) prior to 28.0.0.161
• Red Hat Enterprise Linux 6 Desktop, Server, and Workstation (Flash Player plugin packages)

Patched:

• Adobe Flash Player 28.0.0.161 and later

Remediation

1. Upgrade: Update Adobe Flash Player to version 28.0.0.161 or later. Adobe released APSB18-03 to address this vulnerability.
2. Disable or Remove Flash: Since Adobe Flash Player reached end-of-life in December 2020, the strongest compensating control is complete removal or disablement of the Flash Player plugin and ActiveX control.
3. Browser Hardening: Block Flash content in browsers and email clients; disable automatic execution of embedded objects in Microsoft Office.
4. Application Whitelisting: Restrict execution of untrusted Office documents and browser plugins to reduce attack surface.

Detection

• Monitor for Flash Player processes spawned by Microsoft Office applications (e.g., winword.exe launching Flash-related processes).
• Inspect Office documents for embedded ActiveX or Flash objects using sandbox detonation or static analysis.
• Correlate endpoint telemetry with known malicious indicators from campaigns leveraging this vulnerability (see FireEye, Talos, and Trend Micro reporting).
• Review network logs for anomalous outbound connections from Flash Player processes.

Assessment

This vulnerability carries an EPSS score of 0.89618 (99.77th percentile), indicating a very high probability of exploitation in the wild. It is confirmed as a Known Exploited Vulnerability (KEV) by CISA and listed in the EU Exploited Vulnerability Database (EUVD-2018-16663) since 2021-11-03.

Key lessons:

1. Timely patching matters: The gap between in-the-wild exploitation (January 2018) and patch availability (early February 2018) provided a critical window for defenders. Organizations with mature patch management reduced exposure.
2. Legacy software risk: The continued presence of Flash Player long after its EOL demonstrates how legacy components with complex codebases can become persistent liabilities. Proactive removal of deprecated software is a high-value defensive measure.

References

• https://helpx.adobe.com/security/products/flash-player/apsb18-03.html
• https://www.fireeye.com/blog/threat-research/2018/02/attacks-leveraging-adobe-zero-day.html
• https://blog.talosintelligence.com/2018/02/group-123-goes-wild.html
• https://www.trendmicro.com/vinfo/us/security/news/vulnerabilities-and-exploits/north-korean-hackers-allegedly-exploit-adobe-flash-player-vulnerability-cve-2018-4878-against-south-korean-targets
• https://threatpost.com/adobe-flash-player-zero-day-spotted-in-the-wild/129742/
• https://securingtomorrow.mcafee.com/mcafee-labs/hackers-bypassed-adobe-flash-protection-mechanism/
• https://blog.morphisec.com/flash-exploit-cve-2018-4878-spotted-in-the-wild-massive-malspam-campaign
• https://access.redhat.com/errata/RHSA-2018:0285
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2018-4878
• https://github.com/cisagov/vulnrichment/issues/196