CVE-2026-21358: Adobe InDesign Buffer Overflow Vulnerability

CVE-2026-21358 Overview

CVE-2026-21358 is a Heap-based Buffer Overflow vulnerability affecting Adobe InDesign Desktop that could result in application denial-of-service. An attacker could exploit this vulnerability to crash the application, causing disruption to services. Exploitation of this issue requires user interaction in that a victim must open a malicious file.

Critical Impact

Successful exploitation allows attackers to crash Adobe InDesign Desktop by triggering a heap-based buffer overflow through a maliciously crafted file, resulting in denial of service and potential data loss from unsaved work.

Affected Products

• Adobe InDesign Desktop version 21.1 and earlier
• Adobe InDesign Desktop version 20.5.1 and earlier
• Affected on both Apple macOS and Microsoft Windows operating systems

Discovery Timeline

• 2026-02-10 - CVE-2026-21358 published to NVD
• 2026-02-11 - Last updated in NVD database

Technical Details for CVE-2026-21358

Vulnerability Analysis

This vulnerability is classified as a Heap-based Buffer Overflow (CWE-122) and Out-of-Bounds Write (CWE-787). The flaw exists in Adobe InDesign Desktop's file parsing functionality, where insufficient boundary checking allows data to be written beyond the allocated heap buffer when processing specially crafted documents.

The vulnerability requires local access and user interaction to exploit—a victim must be tricked into opening a malicious InDesign file. While the vulnerability does not enable code execution or data exfiltration according to the current assessment, it can reliably crash the application, causing high availability impact.

Root Cause

The root cause of CVE-2026-21358 stems from improper memory management in Adobe InDesign Desktop's document parsing routines. When processing certain malformed document structures, the application fails to properly validate input lengths before copying data into heap-allocated buffers. This allows an attacker to craft a file that triggers an out-of-bounds write operation, corrupting heap memory and causing the application to crash.

Attack Vector

The attack vector for this vulnerability is local, requiring user interaction. An attacker would typically deliver the malicious InDesign file through:

1. Phishing emails with malicious .indd file attachments
2. Compromised file-sharing platforms or collaboration services
3. Social engineering tactics convincing users to download and open the file
4. Supply chain attacks through compromised design assets or templates

When a victim opens the crafted document in a vulnerable version of InDesign Desktop, the heap-based buffer overflow is triggered, causing the application to terminate unexpectedly. This can result in loss of unsaved work and disruption to design workflows.

Detection Methods for CVE-2026-21358

Indicators of Compromise

• Unexpected InDesign Desktop application crashes, particularly when opening files from external or untrusted sources
• Crash reports indicating heap corruption or memory access violations in InDesign processes
• Suspicious .indd or .indt files received from unknown sources or unusual delivery methods
• Windows Event Viewer or macOS Console logs showing application faults in InDesign.exe or Adobe InDesign processes

Detection Strategies

• Monitor endpoint detection systems for abnormal InDesign process terminations that may indicate exploitation attempts
• Implement file scanning solutions to analyze InDesign documents for malformed or suspicious structures before user access
• Deploy application crash monitoring to identify patterns of InDesign failures that could indicate targeted exploitation
• Use sandboxed environments to pre-screen InDesign files received from external parties

Monitoring Recommendations

• Enable application crash reporting and centralize crash dump collection for security analysis
• Monitor for unusual volumes of InDesign files being received via email or file transfer
• Configure SentinelOne to alert on repeated application crashes that may indicate exploitation attempts
• Track user reports of InDesign instability following the opening of externally sourced files

How to Mitigate CVE-2026-21358

Immediate Actions Required

• Update Adobe InDesign Desktop to the latest patched version immediately
• Advise users to avoid opening InDesign files from untrusted or unknown sources until patching is complete
• Implement email attachment filtering to quarantine or scan .indd files from external senders
• Review and restrict file-sharing permissions for InDesign document types in collaborative environments

Patch Information

Adobe has released a security update addressing this vulnerability. Organizations should apply the patch referenced in Adobe InDesign Security Advisory APSB26-17. The advisory provides details on fixed versions for both Windows and macOS platforms.

Users should update to the latest available version through Adobe Creative Cloud or the Adobe Admin Console for enterprise deployments. Verify successful patch installation by checking the application version in InDesign's "About" dialog.

Workarounds

• Configure email security gateways to block or quarantine InDesign files (.indd, .indt, .idml) from external sources pending patch deployment
• Implement a policy requiring users to verify the legitimacy of InDesign files with senders before opening
• Use Protected View or sandboxed environments where available when opening files from untrusted sources
• Consider temporarily restricting InDesign usage to internal, verified documents until the patch is applied

Organizations should prioritize patching as the primary remediation strategy, using workarounds only as temporary measures to reduce exposure.