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FirefoxWeb browser · Mozilla

CVE-2023-23602

MEDIUM · 6.5 CVSS v3.1 Published 2023-06-02
Fix available
A fix is available. Upgrade to 102.7 / 109.0 or later.
See remediation →
72/100
Remediation priority · Elevated
Remotely reachable No privileges

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 mishandled security check when creating a WebSocket in a WebWorker caused the Content Security Policy connect-src header to be ignored. This could lead to connections to restricted origins from inside WebWorkers. This vulnerability affects Firefox < 109, Firefox ESR < 102.7, and Thunderbird < 102.7.

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 · high confidence

A security check is mishandled when creating WebSockets inside WebWorkers, causing the Content Security Policy connect-src directive to be bypassed. This allows WebWorkers to establish connections to origins that should be restricted by CSP.

MitigationUpgrade affected endpoints to Firefox 109+, Firefox ESR 102.7+, or Thunderbird 102.7+ to apply the vendor patch.

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

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
FirefoxWeb browser
Affected:< 109.0
Firefox EsrWeb browser
Affected:< 102.7
ThunderbirdApplication
Affected:< 102.7

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
Required
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

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

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. Check Firefox version
    Open Firefox, go to Help > About Firefox (or navigate to about:support). Note the version number displayed.
    Affected if The version is below 109.0 (for standard Firefox) or below 102.7 (for Firefox ESR)
  2. Check Thunderbird version
    Open Thunderbird, go to Help > About Thunderbird. Note the version number displayed.
    Affected if The version is below 102.7
  3. Verify WebWorker usage in web content
    Inspect web application code or use browser developer tools (Application tab > Service Workers/Web Workers) to determine if the application creates WebWorkers that initiate WebSocket connections.
    Affected if WebWorkers are used to establish WebSocket connections from web content
  4. Check Content Security Policy configuration
    In the affected browser, navigate to the target web application. Open Developer Tools (F12), go to the Console tab, and evaluate: console.log(document.securityPolicyViolations) or inspect response headers for 'Content-Security-Policy' header containing connect-src directive.
    Affected if The web application uses a CSP policy with connect-src restrictions and loads content in the affected browser version

You are affected if you run Firefox < 109.0 (or ESR < 102.7) or Thunderbird < 102.7 AND your web application uses WebWorkers that create WebSocket connections while enforcing a CSP connect-src policy.

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
Upgrade available Upgrade to 102.7 / 109.0 or later
Fixed in 102.7109.0
Interim mitigation

Upgrade affected endpoints to Firefox 109+, Firefox ESR 102.7+, or Thunderbird 102.7+ to apply the vendor patch.

Recommended fix High confidence

Firefox 109.0, Firefox ESR 102.7, or Thunderbird 102.7 (depending on product)

  1. 1. Backup any critical data and configurations
  2. 2. Close all instances of Firefox, Firefox ESR, or Thunderbird
  3. 3. Download the latest version from the official Mozilla website (www.mozilla.org) or use your system's package manager
  4. 4. Install the update: For Firefox, upgrade to version 109.0 or later
  5. 5. For Firefox ESR users, upgrade to version 102.7 or later
  6. 6. For Thunderbird users, upgrade to version 102.7 or later
  7. 7. Verify the installed version matches or exceeds the fixed release (Help > About Firefox/Thunderbird)
  8. 8. Restart the application and verify WebSocket connections in WebWorkers respect CSP connect-src policies
Caveat Minimal; security patches typically have no breaking changes. Users should test any WebWorker-based WebSocket functionality after upgrade.

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

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Testing1.0 h
  • Review / QA1.0 h
3.0 hours of engineering $750
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,200.

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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-2023-23602 in production — separate from our analysis above.

No notes yet

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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