CVE-2026-55886 Overview
Jodit Editor, a WYSIWYG editor written in pure TypeScript with file and image editing capabilities, contains a prototype pollution vulnerability in versions prior to 4.12.26. The flaw resides in Jodit.modules.Helpers.set(chain, value, obj), which walks a dot-separated key chain and creates each path segment without filtering prototype-mutating keys. A chain containing __proto__, constructor, or prototype allows the final assignment to mutate Object.prototype. Applications that pass user-controlled key paths into this helper function are vulnerable to unexpected property injection, logic bypass, denial of service, or downstream security issues. The issue is tracked under [CWE-1321] and has been fixed in version 4.12.26.
Critical Impact
Attackers supplying crafted key paths can pollute Object.prototype, enabling logic bypass, denial of service, or secondary exploitation in downstream code paths.
Affected Products
- Jodit Editor versions prior to 4.12.26
- Applications embedding Jodit Editor that expose Jodit.modules.Helpers.set() to user-controlled input
- Web applications built with vulnerable Jodit versions in their dependency tree
Discovery Timeline
- 2026-07-01 - CVE-2026-55886 published to NVD
- 2026-07-02 - Last updated in NVD database
Technical Details for CVE-2026-55886
Vulnerability Analysis
The vulnerability is a prototype pollution flaw in the Jodit Editor helper module. The set(chain, value, obj) function accepts a dot-separated chain string, splits it into path segments, and traverses the target object. For each segment, the function creates the property if missing and descends into it. The traversal logic does not blocklist keys that reference the JavaScript prototype chain.
When an attacker supplies a chain such as __proto__.polluted or constructor.prototype.polluted, the traversal reaches Object.prototype. The final assignment then writes an attacker-controlled value onto the base object prototype. Every JavaScript object in the runtime inherits the injected property.
Consequences depend on the host application. Downstream code that reads properties without hasOwnProperty checks may take attacker-chosen branches, bypass authorization logic, or crash on unexpected values. In server-side rendered contexts, polluted prototypes can enable secondary vulnerabilities such as remote code execution through template engines or gadget chains.
Root Cause
The helper function fails to filter dangerous keys (__proto__, constructor, prototype) during recursive property assignment. This is a classic implementation of [CWE-1321] Improperly Controlled Modification of Object Prototype Attributes.
Attack Vector
Exploitation requires the host application to pass user-controlled or partially user-controlled input to Jodit.modules.Helpers.set() as the chain argument. The attack occurs over the network with low complexity but requires the application to expose the vulnerable helper. Refer to the GitHub Security Advisory GHSA-vpmm-x3fm-qr5c for technical details.
Detection Methods for CVE-2026-55886
Indicators of Compromise
- Request parameters, JSON bodies, or query strings containing the tokens __proto__, constructor.prototype, or prototype. in key path values
- Unexpected properties appearing on generic JavaScript objects during runtime
- Client-side or server-side exceptions triggered by unexpected inherited properties
Detection Strategies
- Perform Software Composition Analysis (SCA) to identify Jodit Editor versions below 4.12.26 in application dependencies
- Inspect application code for calls to Jodit.modules.Helpers.set() that accept user-controlled key paths
- Deploy Web Application Firewall (WAF) rules that flag payloads containing prototype-mutating tokens in request bodies
Monitoring Recommendations
- Log and alert on HTTP requests containing __proto__, constructor, or prototype substrings within JSON keys or path values
- Monitor Node.js or browser runtime errors indicating unexpected property access on core objects
- Track outbound behavior from applications embedding Jodit for anomalies that may indicate successful prototype pollution
How to Mitigate CVE-2026-55886
Immediate Actions Required
- Upgrade Jodit Editor to version 4.12.26 or later across all applications and build pipelines
- Audit application code for any invocation of Jodit.modules.Helpers.set() that receives untrusted input
- Sanitize or reject key chains containing __proto__, constructor, or prototype before passing them to the helper
Patch Information
The maintainers fixed the issue in Jodit Editor version 4.12.26. The patched helper filters prototype-mutating keys during chain traversal. Review the GitHub Security Advisory GHSA-vpmm-x3fm-qr5c for the official fix reference.
Workarounds
- Wrap calls to Jodit.modules.Helpers.set() with a validator that rejects chains containing __proto__, constructor, or prototype
- Use Object.create(null) for target objects passed to the helper to eliminate the prototype chain
- Freeze Object.prototype with Object.freeze(Object.prototype) during application initialization to block runtime mutation
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
