Protocol-handler disclosure via image-error timing oracle
Published Jun 11, 2024 · Updated Mar 26, 2025
Timing disclosure in Firefox before 127, Firefox ESR before 115.12, and Thunderbird before 115.12 allows remote attackers to infer protocol handlers. nsExternalProtocolHandler::NewChannel returned early when no handler existed, so an image element's onerror delay differed between registered and unsupported schemes. A user must load attacker-controlled content; repeated timing measurements reveal which external applications handle tested schemes without exposing their data.
Summary
What happened
Timing disclosure in Firefox before 127, Firefox ESR before 115.12, and Thunderbird before 115.12 allows remote attackers to infer protocol handlers. nsExternalProtocolHandler::NewChannel returned early when no handler existed, so an image element's onerror delay differed between registered and unsupported schemes. A user must load attacker-controlled content; repeated timing measurements reveal which external applications handle tested schemes without exposing their data.
The record
- CVE
- CVE-2024-5690
- Published
- Jun 11, 2024
- Updated
- Mar 26, 2025
- Vendor
- Mozilla
- Product
- Firefox
- Classifications
- CWE-203, T1592.002
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jun 11, 2024CVE publishedPublication date reported by the CVE source.
- Mar 26, 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 <127
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
- poc_img.html timing demonstrationproof 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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