Restricted-origin connections via omitted WebWorker CSP check
Published Jun 2, 2023 · Updated Dec 18, 2025
CSP bypass in Mozilla Firefox before 109, Firefox ESR before 102.7, and Thunderbird before 102.7 lets remote attackers reach restricted origins. WebSocket creation in a WebWorker omitted the worker's connect-src policy check, so a script could establish a connection that the delivered CSP prohibited. A user must load attacker-controlled web content or another browser-like context that executes the worker; ordinary Thunderbird email reading disables scripting.
Summary
What happened
CSP bypass in Mozilla Firefox before 109, Firefox ESR before 102.7, and Thunderbird before 102.7 lets remote attackers reach restricted origins. WebSocket creation in a WebWorker omitted the worker's connect-src policy check, so a script could establish a connection that the delivered CSP prohibited. A user must load attacker-controlled web content or another browser-like context that executes the worker; ordinary Thunderbird email reading disables scripting.
The record
- CVE
- CVE-2023-23602
- Published
- Jun 2, 2023
- Updated
- Dec 18, 2025
- Vendor
- Mozilla
- Product
- Firefox
- Classifications
- Unavailable
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jun 2, 2023CVE publishedPublication date reported by the CVE source.
- Dec 18, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=unspecified <109
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
No sourced classifications are available.
Public exploit references
- WebWorker WebSocket CSP reproduction pageproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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