CVE-2025-4921 is a low severity vulnerability with a CVSS score of 0.0. No known public exploits at this time.
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Very low probability of exploitation
EPSS predicts the probability of exploitation in the next 30 days based on real-world threat data, complementing CVSS severity scores with actual risk assessment.
An attacker was able to perform an out-of-bounds read or write on a JavaScript object by confusing array index sizes. This vulnerability affects Firefox < 138.0.4 and Firefox ESR < 128.10.1.