High

Integer Underflow RCE in Adobe InCopy

IdentifiersCVE-2025-21156CWE-191· Integer Underflow (Wrap or…

CVE-2025-21156 is a critical integer underflow vulnerability in Adobe InCopy affecting version 20.0 and 19.5.1 and earlier on Windows and macOS. The flaw is classified as CWE-191 and can be triggered when the application processes a specially crafted malicious document. Successful exploitation can result in arbitrary code execution in the context of the current user. The issue is associated with file parsing and requires the victim to open a malicious file.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation allows arbitrary code execution with the privileges of the logged-in user running Adobe InCopy. This can lead to full compromise of confidentiality, integrity, and availability for data and resources accessible to that user account, including installation of malware, modification of data, and disruption of system operation.

Mitigation

If you can’t patch tonight, do this now.

Apply the vendor patches immediately. Until updates are fully deployed, reduce exposure by preventing users from opening untrusted or unexpected InCopy documents, especially those received through email or external sharing channels. In managed environments, restrict execution context where possible and use centralized software deployment to ensure all endpoints are updated to the fixed versions.

Remediation

Patch, then assume compromise.

Upgrade Adobe InCopy to a fixed release. Adobe indicates that version 20.1 addresses the issue for the 20.x branch and version 19.5.2 addresses the issue for the 19.x branch. Organizations should deploy the vendor-provided security updates across affected Windows and macOS systems as a priority.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType

AdobeIncopyapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

2 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

2 SOURCESView more in app

csirt skNews

Feb 17, 2025

Kritické bezpečnostné zraniteľnosti v produktoch Adobe | CSIRT.SK

Adobe InCopy integer underflow vulnerability that can lead to remote code execution and full compromise of confidentiality, integrity, and availability.

adobe-security-bulletinsNews

Feb 11, 2025

Adobe Security Bulletin

A critical integer underflow vulnerability in Adobe InCopy (CVE-2025-21156) that could allow arbitrary code execution if exploited.

What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.

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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity