Cross-origin data disclosure via unchecked favicon fetch
Published Mar 31, 2021 · Updated Aug 3, 2024
Origin validation failure in Mozilla Firefox before 87 allows attackers to read cross-origin resources through a malicious extension. The search engine manager fetches an absolute favicon URL and converts the response into an extension-readable data URI without checking its origin or actual content type. Exploitation requires an installed extension with search permission; cookie-free requests limit disclosure to local-network or IP-authenticated resources.
Summary
What happened
Origin validation failure in Mozilla Firefox before 87 allows attackers to read cross-origin resources through a malicious extension. The search engine manager fetches an absolute favicon URL and converts the response into an extension-readable data URI without checking its origin or actual content type. Exploitation requires an installed extension with search permission; cookie-free requests limit disclosure to local-network or IP-authenticated resources.
The record
- CVE
- CVE-2021-23986
- Published
- Mar 31, 2021
- Updated
- Aug 3, 2024
- Vendor
- Mozilla
- Product
- Firefox
- Classifications
- CWE-346
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 31, 2021CVE publishedPublication date reported by the CVE source.
- Aug 3, 2024Record 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 <87
What conditions does exploitation require?
What is affected?
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
Public exploit references
- Signed cross-origin-read extension proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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