CVE-2026-21357: Adobe InDesign Buffer Overflow Vulnerability

CVE-2026-21357 Overview

CVE-2026-21357 is a Heap-based Buffer Overflow vulnerability affecting Adobe InDesign Desktop that could result in arbitrary code execution in the context of the current user. This memory corruption flaw allows attackers to potentially take control of affected systems when a user opens a specially crafted malicious file. The vulnerability impacts multiple versions of InDesign across both Windows and macOS platforms.

Critical Impact

Successful exploitation of this heap-based buffer overflow could allow an attacker to execute arbitrary code with the privileges of the current user, potentially leading to complete system compromise. User interaction is required, as victims must be tricked into opening a malicious document.

Affected Products

• Adobe InDesign versions 21.1 and earlier
• Adobe InDesign versions 20.5.1 and earlier
• Platforms: Microsoft Windows and Apple macOS

Discovery Timeline

• February 10, 2026 - CVE-2026-21357 published to NVD
• February 11, 2026 - Last updated in NVD database

Technical Details for CVE-2026-21357

Vulnerability Analysis

This vulnerability is classified under CWE-122 (Heap-based Buffer Overflow) and CWE-787 (Out-of-bounds Write). When Adobe InDesign processes a maliciously crafted file, improper bounds checking allows data to be written beyond the allocated heap buffer. This memory corruption can be leveraged by an attacker to overwrite critical heap metadata or adjacent memory structures, ultimately enabling arbitrary code execution.

The attack requires local access and user interaction, meaning the victim must be induced to open a specially crafted InDesign document (.indd file) or related file format processed by InDesign. Once opened, the malformed data triggers the buffer overflow condition during parsing or rendering operations.

Root Cause

The root cause of CVE-2026-21357 lies in insufficient validation of input data sizes before copying content into heap-allocated buffers within InDesign's file parsing routines. When processing document elements, the application fails to properly verify that the incoming data fits within the destination buffer's allocated size, resulting in a heap-based buffer overflow condition.

Attack Vector

The attack vector for this vulnerability is local, requiring user interaction. An attacker would typically:

1. Craft a malicious InDesign document containing specially structured data designed to trigger the heap overflow
2. Distribute the malicious file via email attachments, file sharing services, or compromised websites
3. Social engineer the victim into opening the document in a vulnerable version of Adobe InDesign
4. Upon opening, the malformed data overflows the heap buffer, corrupting adjacent memory
5. Carefully crafted overflow data can redirect execution flow to attacker-controlled code

The vulnerability exploits the trust users place in document files, particularly in creative workflow environments where InDesign files are routinely shared between designers, publishers, and print service providers.

Detection Methods for CVE-2026-21357

Indicators of Compromise

• Unexpected crashes or abnormal termination of Adobe InDesign processes
• Memory access violations or heap corruption errors in InDesign logs
• Suspicious .indd or InDesign-related files received from unknown sources
• Unusual process spawning or network connections originating from InDesign

Detection Strategies

• Monitor for heap corruption signatures and memory access violations in Adobe InDesign process
• Implement file inspection rules to detect anomalous InDesign document structures
• Deploy endpoint detection rules to identify exploitation attempts targeting Adobe Creative Cloud applications
• Enable application crash monitoring and analyze crash dumps for exploitation patterns

Monitoring Recommendations

• Enable verbose logging for Adobe InDesign and monitor for parsing errors or memory-related warnings
• Configure endpoint protection to alert on suspicious behavior from InDesign processes, such as spawning child processes or network connections
• Implement email gateway filtering to quarantine potentially malicious InDesign attachments from untrusted sources
• Monitor file access patterns for InDesign documents, particularly those recently downloaded or received via email

How to Mitigate CVE-2026-21357

Immediate Actions Required

• Update Adobe InDesign Desktop to the latest patched version immediately
• Restrict opening InDesign files from untrusted or unknown sources until patches are applied
• Implement application whitelisting to prevent unauthorized code execution
• Educate users about the risks of opening unsolicited InDesign documents

Patch Information

Adobe has released security updates addressing this vulnerability as documented in Adobe Security Advisory APSB26-17. Organizations should update to the latest available versions of InDesign Desktop through Adobe Creative Cloud or the Adobe Admin Console. The advisory provides specific version numbers that contain the security fix.

Workarounds

• If immediate patching is not possible, restrict InDesign file handling to only trusted, verified sources
• Consider using Protected View or sandboxed environments when opening InDesign files from external parties
• Implement network segmentation to limit the impact of potential compromise
• Disable automatic file preview features in file explorers and email clients for InDesign file types

# Verify InDesign version on macOS
mdls -name kMDItemVersion "/Applications/Adobe InDesign 2026/Adobe InDesign 2026.app"

# Check running InDesign processes for monitoring
ps aux | grep -i "InDesign"