CVE-2025-6492 Overview
CVE-2025-6492 is an inefficient regular expression complexity vulnerability [CWE-400] in the MarkText markdown editor through version 0.17.1. The flaw resides in the getRecommendTitleFromMarkdownString function within marktext/src/main/utils/index.js. A crafted input string triggers catastrophic backtracking in a regular expression, causing excessive CPU consumption. The attack is exploitable remotely without authentication or user interaction, and a public exploit disclosure exists. The impact is limited to availability degradation of the affected process. MarkText is an open-source Electron-based markdown editor used across Windows, macOS, and Linux platforms.
Critical Impact
Remote unauthenticated attackers can trigger a Regular Expression Denial of Service (ReDoS) condition by supplying malicious markdown content processed by MarkText.
Affected Products
- MarkText versions up to and including 0.17.1
- File: marktext/src/main/utils/index.js
- Function: getRecommendTitleFromMarkdownString
Discovery Timeline
- 2025-06-22 - CVE-2025-6492 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-6492
Vulnerability Analysis
The vulnerability is classified as inefficient regular expression complexity [CWE-400], commonly known as a Regular Expression Denial of Service (ReDoS). The affected function getRecommendTitleFromMarkdownString in marktext/src/main/utils/index.js parses markdown input to derive a recommended title. The regular expression used for this parsing contains overlapping or ambiguous quantifiers. When an attacker supplies a specially crafted string, the regex engine enters catastrophic backtracking. Processing time grows non-linearly with input length, blocking the Node.js event loop in the Electron main process.
Root Cause
The root cause is a regex pattern that permits multiple ways to match the same substring. Node.js uses a backtracking regex engine, so ambiguity in the pattern forces exponential state exploration on non-matching inputs. The function accepts markdown content without input length limits or timeout controls before evaluating the pattern. See the GitHub Pull Request 3952 for the corrective change and the GitHub Test Specification Code for the demonstrating test case.
Attack Vector
An attacker delivers a malicious markdown document to a victim who opens it in MarkText, or supplies crafted content through any workflow that feeds strings into getRecommendTitleFromMarkdownString. Processing the crafted input consumes CPU cycles and hangs the application. No authentication, credentials, or interactive privilege is required beyond opening or importing the document. The vulnerability does not compromise confidentiality or integrity.
No verified public proof-of-concept code is included in this advisory. Refer to the VulDB #313609 Details entry and the linked test specification for the pattern that demonstrates the backtracking condition.
Detection Methods for CVE-2025-6492
Indicators of Compromise
- Sustained 100% CPU utilization by the MarkText process (marktext.exe, MarkText, or marktext) with no user activity.
- MarkText windows becoming unresponsive shortly after opening or importing a markdown file from an untrusted source.
- Suspicious .md files containing unusually long repeating character sequences or crafted title/heading structures.
Detection Strategies
- Monitor endpoint telemetry for the MarkText process consuming excessive CPU for extended periods.
- Inspect markdown files delivered via email, file shares, or downloads for oversized inputs or repeating patterns that could trigger backtracking.
- Track installed versions of MarkText across the environment and flag any at or below 0.17.1.
Monitoring Recommendations
- Alert on repeated crashes or hangs of the MarkText process across multiple endpoints, which may indicate targeted delivery of malicious documents.
- Log file-open events for .md files sourced from external channels and correlate with process performance metrics.
- Review the application inventory for outdated MarkText installations on developer and technical writer workstations.
How to Mitigate CVE-2025-6492
Immediate Actions Required
- Identify all endpoints with MarkText version 0.17.1 or earlier and prioritize them for update or removal.
- Restrict opening markdown files from untrusted or external sources until patching is complete.
- Terminate any hung MarkText process consuming high CPU and preserve the offending file for analysis.
Patch Information
A fix has been proposed upstream in GitHub Pull Request 3952. The patch addresses the regex in getRecommendTitleFromMarkdownString to eliminate the ambiguous quantifier that enables backtracking. Track the MarkText repository releases for the version that incorporates this change and upgrade once available. Additional context is available in the VulDB #313609 CTI Info entry.
Workarounds
- Avoid opening markdown files received from untrusted sources in MarkText until an upstream release including the fix is deployed.
- Pre-process markdown content through a length-limited sanitizer before passing it to MarkText.
- Consider temporarily switching to an alternative markdown editor for handling externally sourced content.
- Apply application allowlisting or file-size limits at the endpoint to reduce exposure to oversized markdown payloads.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
