CVE-2026-21321: Adobe After Effects RCE Vulnerability

CVE-2026-21321 Overview

CVE-2026-21321 is an Integer Overflow or Wraparound vulnerability affecting Adobe After Effects versions 25.6 and earlier. This vulnerability could allow an attacker to achieve arbitrary code execution in the context of the current user. Successful exploitation requires user interaction, specifically that a victim must open a malicious file crafted to trigger the integer overflow condition.

Critical Impact

Successful exploitation enables arbitrary code execution with user-level privileges on both Windows and macOS systems through maliciously crafted files.

Affected Products

• Adobe After Effects versions 25.6 and earlier
• Apple macOS (all supported versions running vulnerable After Effects)
• Microsoft Windows (all supported versions running vulnerable After Effects)

Discovery Timeline

• 2026-02-10 - CVE-2026-21321 published to NVD
• 2026-02-11 - Last updated in NVD database

Technical Details for CVE-2026-21321

Vulnerability Analysis

This vulnerability is classified as CWE-190 (Integer Overflow or Wraparound). Integer overflow vulnerabilities occur when arithmetic operations produce a result that exceeds the maximum value that can be stored in the allocated memory space. In Adobe After Effects, this condition can be triggered when processing specially crafted project files or media assets.

When an integer overflow occurs, the resulting value wraps around to a much smaller number than expected. This can lead to undersized buffer allocations, which subsequently result in heap or stack buffer overflows when the application attempts to write data into these insufficient memory regions. An attacker can leverage this memory corruption to achieve arbitrary code execution.

Root Cause

The vulnerability stems from insufficient validation of numeric input values before performing arithmetic operations within After Effects' file parsing routines. When processing certain data structures in project files, the application fails to verify that calculated buffer sizes remain within acceptable bounds, allowing integer wraparound to occur.

Attack Vector

The attack requires local access and user interaction. An attacker must craft a malicious After Effects project file (.aep) or supported media file that contains carefully constructed values designed to trigger the integer overflow. When a victim opens this file, the overflow condition is triggered during parsing, leading to memory corruption and potential code execution with the privileges of the user running After Effects.

The vulnerability mechanism involves numeric operations during file parsing that can overflow when processing malformed data structures. When the application calculates memory allocation sizes, specially crafted values can cause the computed size to wrap around, resulting in smaller-than-expected buffer allocations. Subsequent write operations then overflow these buffers, corrupting adjacent memory and potentially allowing attacker-controlled code execution. For technical implementation details, refer to the Adobe Security Advisory APSB26-15.

Detection Methods for CVE-2026-21321

Indicators of Compromise

• Unexpected crashes or abnormal termination of Adobe After Effects when opening project files
• After Effects attempting to allocate unusually small memory buffers before crashing
• Suspicious .aep or media files from untrusted sources that cause application instability
• System event logs showing memory access violations originating from After Effects processes

Detection Strategies

• Monitor for Adobe After Effects process crashes accompanied by memory corruption indicators
• Implement file integrity monitoring on After Effects project directories
• Deploy endpoint detection rules to identify After Effects processes spawning unexpected child processes
• Use application whitelisting to detect code execution from non-standard locations following After Effects crashes

Monitoring Recommendations

• Enable enhanced logging for Adobe Creative Cloud applications
• Monitor user endpoints for After Effects processing files from email attachments or external downloads
• Configure security tools to alert on After Effects accessing suspicious or recently downloaded files
• Implement behavioral analysis to detect post-exploitation activity following After Effects execution

How to Mitigate CVE-2026-21321

Immediate Actions Required

• Update Adobe After Effects to a version newer than 25.6 as soon as a patch is available
• Advise users to avoid opening After Effects files from untrusted or unknown sources
• Implement email attachment filtering to quarantine After Effects project files pending security review
• Enable Adobe's automatic update functionality to ensure timely patch deployment

Patch Information

Adobe has released security advisory APSB26-15 addressing this vulnerability. Users should apply the latest After Effects update available through Adobe Creative Cloud. Verify your installation is updated beyond version 25.6 to ensure protection against this vulnerability.

Workarounds

• Restrict After Effects to process only files from trusted internal sources until patching is complete
• Consider disabling After Effects temporarily on high-risk systems if the application is not business-critical
• Implement network segmentation to isolate creative workstations from sensitive systems
• Train users on the risks of opening unsolicited project files and establish verification procedures for external files

# Verify Adobe After Effects version on Windows
# Navigate to Help > About After Effects to confirm version is newer than 25.6

# Enable automatic updates in Creative Cloud
# Open Creative Cloud Desktop > Preferences > General > Enable "Auto-update"