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CVE-2025-5266

MEDIUMCVSS 4.3/10EPSS 0.26%

Last modified

CVE-2025-5266 is a medium-severity vulnerability rated 4.3/10 on the CVSS scale. Script elements loading cross-origin resources generated load and error events which leaked information enabling XS-Leaks attacks. This vulnerability was fixed in Firefox 139, Firefox ESR 128.11, Thunderbird 139, and Thunderbird 128.11.. EPSS estimates a 0.26% chance of exploitation in the next 30 days.

Description

Script elements loading cross-origin resources generated load and error events which leaked information enabling XS-Leaks attacks. This vulnerability was fixed in Firefox 139, Firefox ESR 128.11, Thunderbird 139, and Thunderbird 128.11.

Metrics

CVSS 3.1
4.3/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

EPSS Probability
0.26%

17.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
MozillaFirefox< 128.11.0
MozillaFirefox< 139.0

References

Timeline

Published
Last Modified
Status
Modified

Frequently Asked Questions

What is CVE-2025-5266?
Script elements loading cross-origin resources generated load and error events which leaked information enabling XS-Leaks attacks. This vulnerability was fixed in Firefox 139, Firefox ESR 128.11, Thunderbird 139, and Thunderbird 128.11.
How severe is CVE-2025-5266?
CVE-2025-5266 has a CVSS score of 4.3/10 (MEDIUM severity). The EPSS model estimates a 0.26% probability of exploitation in the next 30 days.
How do I fix CVE-2025-5266?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2025-5266?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST