CVE-2021-28550

What is this vulnerability?

CVE-2021-28550 is categorized as a high Use After Free flaw with a CVSS base score of 8.8. Based on our vulnerability intelligence, this issue occurs when the application fails to securely handle untrusted data boundaries.

Acrobat Reader DC versions versions 2021.001.20150 (and earlier), 2020.001.30020 (and earlier) and 2017.011.30194 (and earlier) are affected by a Use After Free vulnerability. An unauthenticated attacker could leverage this vulnerability to achieve arbitrary code execution in the context of the current user. Exploitation of this issue requires user interaction in that a victim must open a malicious file.

This architectural defect enables adversaries to bypass intended security controls, directly manipulating the application's execution state or data layer. Immediate strategic intervention is required.

Risk Assessment

Impact on Systems

✅ Remote Code Execution: Attackers can overwrite the instruction pointer to redirect execution to malicious shellcode.

✅ Memory Corruption: Overwriting adjacent memory regions can corrupt critical application state, leading to privilege escalation.

✅ Denial of Service: Triggering segmentation faults results in immediate disruption of critical systems.

How to Fix and Mitigate CVE-2021-28550

1. Apply Vendor Patches Immediately: This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog. Apply updates per vendor instructions.
2. Verify Patch Deployment: Confirm all instances are updated using Precogs continuous monitoring.
3. Review Audit Logs: Investigate historical access logs for indicators of compromise related to this attack surface.
4. Implement Defense-in-Depth: Deploy WAF rules, network segmentation, and endpoint detection to limit blast radius.

Defending with Precogs AI

A use-after-free vulnerability exists in Adobe Acrobat Reader DC when processing specific PDF structures. Attackers trick users into opening crafted documents to execute arbitrary code. Precogs Binary Analysis natively detects complex use-after-free conditions.

Use Precogs to continuously scan your codebase, binaries, APIs, and infrastructure for this vulnerability class and related attack patterns. Our AI-powered detection engine combines static analysis with threat intelligence to identify exploitable weaknesses before attackers do.

Start scanning with Precogs →

Vulnerability Code Signature

Attack Data Flow

Vulnerable Code Pattern

// ❌ VULNERABLE: Use After Free
char *ptr = malloc(256);
free(ptr);
// Taint sink: accessing freed memory
strcpy(ptr, "Exploit payload");

Secure Code Pattern

// ✅ SECURE: Nullifying pointers
char *ptr = malloc(256);
free(ptr);
// Sanitized state: pointer set to NULL
ptr = NULL;

How Precogs Detects This

Precogs Binary SAST engine identifies dangling pointers and complex use-after-free conditions in compiled rendering engines and system libraries.\n