dbcve.org
Uncontrolled Resource ConsumptionWeakness · CWE-400

CVE-2025-6493

MEDIUM · 5.3 CVSS v3.1 Published 2025-06-22
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
62/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A weakness has been identified in CodeMirror up to 5.65.20. Affected is an unknown function of the file mode/markdown/markdown.js of the component Markdown Mode. This manipulation causes inefficient regular expression complexity. It is possible to initiate the attack remotely. The exploit has been made available to the public and could be exploited. Upgrading to version 6.0 is able to address this issue. You should upgrade the affected component. Not all code samples mentioned in the GitHub issue can be found. The repository mentions, that "CodeMirror 6 exists, and is [...] much more actively maintained."

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

CodeMirror versions up to 5.65.20 contain a Regular Expression Denial of Service (ReDoS) vulnerability in the markdown.js mode component. Crafted markdown input triggers inefficient regex complexity, potentially causing excessive CPU consumption or service unavailability.

MitigationUpgrade CodeMirror from version 5.x to version 6.0, which addresses this vulnerability and provides active maintenance support.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Locate CodeMirror installation
    Search your codebase, dependencies (package.json, node_modules), or frontend assets for CodeMirror files. Common locations include node_modules/codemirror, bower_components/codemirror, or bundled JavaScript files.
    Affected if CodeMirror is present in the environment
  2. Determine installed CodeMirror version
    Check package.json for the codemirror package version, or inspect the version comment header in the main codemirror.js or codemirror.min.js file.
    Affected if Version is 5.x up to and including 5.65.20
  3. Verify markdown mode is in use
    Search your codebase for references to the markdown mode: look for 'markdown' in mode loading calls (e.g., editor.setOption('mode', 'markdown')), or check if markdown.js or mode/markdown.js exists in your CodeMirror installation.
    Affected if The markdown mode feature is loaded or configured for use
  4. Confirm vulnerability applicability
    Review the affected version range: this flaw affects CodeMirror 5.x versions up to 5.65.20 specifically in the markdown.js mode component.
    Affected if Running CodeMirror 5.x version 5.65.20 or earlier AND using the markdown mode

A user is affected if CodeMirror version 5.x through 5.65.20 is installed and the markdown mode component is enabled or used to parse user-supplied markdown content.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade CodeMirror from version 5.x to version 6.0, which addresses this vulnerability and provides active maintenance support.

Recommended fix High confidence

CodeMirror 6.x (latest stable release)

  1. Identify all project files that include or reference CodeMirror 5.x library
  2. Update package.json or dependency management file to replace [email protected] with codemirror@^6.0.0 or the latest CodeMirror 6.x version
  3. Run package manager update command (npm install, yarn, or equivalent) to fetch the new version
  4. Review and update any CodeMirror 5 specific initialization code, extensions, or theme references to be compatible with CodeMirror 6 API
  5. Test the application to ensure markdown editing functionality works correctly with the new version
Caveat CodeMirror 6 is a major rewrite with different API and extension system - existing custom modes, themes, and integrations will require migration

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,780
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-6493 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data