Cross-origin JSON disclosure via multipart viewer injection
Published Oct 1, 2024 · Updated Nov 3, 2025
Information disclosure in Mozilla Firefox, Firefox ESR, and Thunderbird allows remote attackers to read cross-origin JSON via multipart responses. The JSONStreamConverter passes later HTML parts into the privileged resource://devtools viewer instead of ignoring them, so their script executes in that origin. Exploitation requires loading attacker-controlled content; Site Isolation limits desktop access to same-site JSON, including exposed request or response headers.
Summary
What happened
Information disclosure in Mozilla Firefox, Firefox ESR, and Thunderbird allows remote attackers to read cross-origin JSON via multipart responses. The JSONStreamConverter passes later HTML parts into the privileged resource://devtools viewer instead of ignoring them, so their script executes in that origin. Exploitation requires loading attacker-controlled content; Site Isolation limits desktop access to same-site JSON, including exposed request or response headers.
The record
- CVE
- CVE-2024-9394
- Published
- Oct 1, 2024
- Updated
- Nov 3, 2025
- Vendor
- Mozilla
- Product
- Firefox
- Classifications
- T1203
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Oct 1, 2024CVE publishedPublication date reported by the CVE source.
- Nov 3, 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 <131
What conditions does exploitation require?
What is affected?
Published CVSS scores
No CVSS assessment is available in this record.
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
Public exploit references
- Bug 1918874 multipart JSON test caseproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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