Is CVE-2025-5266 in the CISA KEV catalog?

No. CVE-2025-5266 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2025-5266?

CVE-2025-5266 has a CVSS v3 base score of 4.3 (MEDIUM).

What is the EPSS score for CVE-2025-5266?

CVE-2025-5266 has an EPSS score of 0.26% (18th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2025-5266?

Upgrade firefox on debian unstable to 139.0-1 or later. Fixes are available for 18 affected products.

CVE & CISA-KEV Catalog

CVE-2025-5266

MEDIUM

4.3

CVSS v3

NVD

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.

CWE-200Information Exposure

How to fix

Remediation Available

firefoxDebian

Fixed in:139.0-1CVE-2025-5266

firefoxRocky

Fixed in:0:128.11.0-1.el10_0RHSA-2025:8341

Fixed in:0:128.11.0-1.el7_9RHSA-2025:9074

Fixed in:0:128.11.0-1.el8_6RHSA-2025:9155

Fixed in:0:128.11.0-1.el8_4RHSA-2025:9076

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8308

Fixed in:0:128.11.0-1.el8_2RHSA-2025:9075

Fixed in:0:128.11.0-1.el8_8RHSA-2025:9077

Fixed in:0:128.11.0-1.el8_6RHSA-2025:9155

Fixed in:0:128.11.0-1.el9_2RHSA-2025:9071

Fixed in:0:128.11.0-1.el9_0RHSA-2025:9073

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8293

Fixed in:0:128.11.0-1.el9_4RHSA-2025:9072

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8293

Fixed in:0:128.11.0-1.el9_4RHSA-2025:9072

Fixed in:0:128.11.0-1.el9_2RHSA-2025:9071

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8293

Fixed in:0:128.11.0-1.el9_2RHSA-2025:9071

Fixed in:0:128.11.0-1.el9_0RHSA-2025:9073

firefoxRed Hat / RHEL

Fixed in:0:128.11.0-1.el10_0RHSA-2025:8341

Fixed in:0:128.11.0-1.el7_9RHSA-2025:9074

Fixed in:0:128.11.0-1.el8_6RHSA-2025:9155

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8308

Fixed in:0:128.11.0-1.el8_4RHSA-2025:9076

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8308

Fixed in:0:128.11.0-1.el8_4RHSA-2025:9076

Fixed in:0:128.11.0-1.el8_2RHSA-2025:9075

Fixed in:0:128.11.0-1.el8_8RHSA-2025:9077

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8293

Fixed in:0:128.11.0-1.el9_4RHSA-2025:9072

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8293

Fixed in:0:128.11.0-1.el9_4RHSA-2025:9072

Fixed in:0:128.11.0-1.el9_0RHSA-2025:9073

Fixed in:0:128.11.0-1.el9_2RHSA-2025:9071

firefox-debuginfoRocky

Fixed in:0:128.11.0-1.el10_0RHSA-2025:8341

Fixed in:0:128.11.0-1.el7_9RHSA-2025:9074

Fixed in:0:128.11.0-1.el8_8RHSA-2025:9077

Fixed in:0:128.11.0-1.el8_2RHSA-2025:9075

Fixed in:0:128.11.0-1.el8_6RHSA-2025:9155

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8308

Fixed in:0:128.11.0-1.el8_4RHSA-2025:9076

Fixed in:0:128.11.0-1.el8_6RHSA-2025:9155

Fixed in:0:128.11.0-1.el8_8RHSA-2025:9077

Fixed in:0:128.11.0-1.el8_6RHSA-2025:9155

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8308

Fixed in:0:128.11.0-1.el8_6RHSA-2025:9155

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8308

Fixed in:0:128.11.0-1.el9_4RHSA-2025:9072

Fixed in:0:128.11.0-1.el9_2RHSA-2025:9071

Fixed in:0:128.11.0-1.el9_0RHSA-2025:9073

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8293

firefox-debuginfoRed Hat / RHEL

Fixed in:0:128.11.0-1.el10_0RHSA-2025:8341

Fixed in:0:128.11.0-1.el7_9RHSA-2025:9074

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8308

Fixed in:0:128.11.0-1.el8_8RHSA-2025:9077

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8308

Fixed in:0:128.11.0-1.el8_2RHSA-2025:9075

Fixed in:0:128.11.0-1.el8_6RHSA-2025:9155

Fixed in:0:128.11.0-1.el8_8RHSA-2025:9077

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8308

Fixed in:0:128.11.0-1.el8_6RHSA-2025:9155

Fixed in:0:128.11.0-1.el8_4RHSA-2025:9076

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8308

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8293

Fixed in:0:128.11.0-1.el9_4RHSA-2025:9072

Fixed in:0:128.11.0-1.el9_2RHSA-2025:9071

Fixed in:0:128.11.0-1.el9_0RHSA-2025:9073

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8293

firefox-debugsourceRocky

Fixed in:0:128.11.0-1.el10_0RHSA-2025:8341

Fixed in:0:128.11.0-1.el8_6RHSA-2025:9155

Fixed in:0:128.11.0-1.el8_4RHSA-2025:9076

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8308

Fixed in:0:128.11.0-1.el8_6RHSA-2025:9155

Fixed in:0:128.11.0-1.el8_2RHSA-2025:9075

Fixed in:0:128.11.0-1.el8_8RHSA-2025:9077

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8293

Fixed in:0:128.11.0-1.el9_0RHSA-2025:9073

Fixed in:0:128.11.0-1.el9_2RHSA-2025:9071

Fixed in:0:128.11.0-1.el9_0RHSA-2025:9073

Fixed in:0:128.11.0-1.el9_4RHSA-2025:9072

Fixed in:0:128.11.0-1.el9_2RHSA-2025:9071

Fixed in:0:128.11.0-1.el9_4RHSA-2025:9072

Fixed in:0:128.11.0-1.el9_0RHSA-2025:9073

Fixed in:0:128.11.0-1.el9_2RHSA-2025:9071

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8293

Fixed in:0:128.11.0-1.el9_4RHSA-2025:9072

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8293

Fixed in:0:128.11.0-1.el9_2RHSA-2025:9071

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8293

Fixed in:0:128.11.0-1.el9_0RHSA-2025:9073

firefox-debugsourceRed Hat / RHEL

Fixed in:0:128.11.0-1.el10_0RHSA-2025:8341

Fixed in:0:128.11.0-1.el8_6RHSA-2025:9155

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8308

Fixed in:0:128.11.0-1.el8_6RHSA-2025:9155

Fixed in:0:128.11.0-1.el8_4RHSA-2025:9076

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8308

Fixed in:0:128.11.0-1.el8_6RHSA-2025:9155

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8308

Fixed in:0:128.11.0-1.el8_8RHSA-2025:9077

Fixed in:0:128.11.0-1.el8_2RHSA-2025:9075

Fixed in:0:128.11.0-1.el8_6RHSA-2025:9155

Fixed in:0:128.11.0-1.el9_4RHSA-2025:9072

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8293

Fixed in:0:128.11.0-1.el9_2RHSA-2025:9071

Fixed in:0:128.11.0-1.el9_0RHSA-2025:9073

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8293

Fixed in:0:128.11.0-1.el9_2RHSA-2025:9071

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8293

Fixed in:0:128.11.0-1.el9_2RHSA-2025:9071

Fixed in:0:128.11.0-1.el9_0RHSA-2025:9073

Fixed in:0:128.11.0-1.el9_4RHSA-2025:9072

firefox-x11Rocky

Fixed in:0:128.11.0-1.el9_2RHSA-2025:9071

Fixed in:0:128.11.0-1.el9_4RHSA-2025:9072

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8293

Fixed in:0:128.11.0-1.el9_4RHSA-2025:9072

Fixed in:0:128.11.0-1.el9_2RHSA-2025:9071

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8293

Fixed in:0:128.11.0-1.el9_2RHSA-2025:9071

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8293

Fixed in:0:128.11.0-1.el9_4RHSA-2025:9072

firefox-x11Red Hat / RHEL

Fixed in:0:128.11.0-1.el9_2RHSA-2025:9071

Fixed in:0:128.11.0-1.el9_4RHSA-2025:9072

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8293

Fixed in:0:128.11.0-1.el9_2RHSA-2025:9071

Fixed in:0:128.11.0-1.el9_4RHSA-2025:9072

Fixed in:0:128.11.0-1.el9_2RHSA-2025:9071

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8293

Fixed in:0:128.11.0-1.el9_2RHSA-2025:9071

Fixed in:0:128.11.0-1.el9_4RHSA-2025:9072

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8293

thunderbirdRed Hat / RHEL

Fixed in:0:128.11.0-1.el10_0RHSA-2025:8608

Fixed in:0:128.11.0-1.el8_2RHSA-2025:8631

Fixed in:0:128.11.0-1.el8_8RHSA-2025:8628

Fixed in:0:128.11.0-1.el8_4RHSA-2025:8630

Fixed in:0:128.11.0-1.el8_8RHSA-2025:8628

Fixed in:0:128.11.0-1.el8_4RHSA-2025:8630

Fixed in:0:128.11.0-1.el8_6RHSA-2025:8629

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8756

Fixed in:0:128.11.0-1.el8_2RHSA-2025:8631

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8607

Fixed in:0:128.11.0-1.el9_0RHSA-2025:8598

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8607

Fixed in:0:128.11.0-1.el9_0RHSA-2025:8598

Fixed in:0:128.11.0-1.el9_4RHSA-2025:8599

Fixed in:0:128.11.0-1.el9_0RHSA-2025:8598

Fixed in:0:128.11.0-1.el9_4RHSA-2025:8599

Fixed in:0:128.11.0-1.el9_2RHSA-2025:8642

Fixed in:0:128.11.0-1.el9_4RHSA-2025:8599

Fixed in:0:128.11.0-1.el9_2RHSA-2025:8642

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8607

Fixed in:0:128.11.0-1.el9_4RHSA-2025:8599

Fixed in:0:128.11.0-1.el9_2RHSA-2025:8642

thunderbirdRocky

Fixed in:0:128.11.0-1.el10_0RHSA-2025:8608

Fixed in:0:128.11.0-1.el8_4RHSA-2025:8630

Fixed in:0:128.11.0-1.el8_8RHSA-2025:8628

Fixed in:0:128.11.0-1.el8_6RHSA-2025:8629

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8756

Fixed in:0:128.11.0-1.el8_2RHSA-2025:8631

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8756

Fixed in:0:128.11.0-1.el8_2RHSA-2025:8631

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8756

Fixed in:0:128.11.0-1.el8_4RHSA-2025:8630

Fixed in:0:128.11.0-1.el9_4RHSA-2025:8599

Fixed in:0:128.11.0-1.el9_2RHSA-2025:8642

Fixed in:0:128.11.0-1.el9_0RHSA-2025:8598

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8607

Fixed in:0:128.11.0-1.el9_2RHSA-2025:8642

Fixed in:0:128.11.0-1.el9_0RHSA-2025:8598

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8607

Fixed in:0:128.11.0-1.el9_0RHSA-2025:8598

Fixed in:0:128.11.0-1.el9_4RHSA-2025:8599

Fixed in:0:128.11.0-1.el9_2RHSA-2025:8642

Fixed in:0:128.11.0-1.el9_4RHSA-2025:8599

Fixed in:0:128.11.0-1.el9_2RHSA-2025:8642

Fixed in:0:128.11.0-1.el9_4RHSA-2025:8599

thunderbird-debuginfoRed Hat / RHEL

Fixed in:0:128.11.0-1.el10_0RHSA-2025:8608

Fixed in:0:128.11.0-1.el8_8RHSA-2025:8628

Fixed in:0:128.11.0-1.el8_4RHSA-2025:8630

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8756

Fixed in:0:128.11.0-1.el8_6RHSA-2025:8629

Fixed in:0:128.11.0-1.el8_2RHSA-2025:8631

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8756

Fixed in:0:128.11.0-1.el8_6RHSA-2025:8629

Fixed in:0:128.11.0-1.el8_8RHSA-2025:8628

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8607

Fixed in:0:128.11.0-1.el9_0RHSA-2025:8598

Fixed in:0:128.11.0-1.el9_4RHSA-2025:8599

Fixed in:0:128.11.0-1.el9_2RHSA-2025:8642

Fixed in:0:128.11.0-1.el9_4RHSA-2025:8599

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8607

thunderbird-debuginfoRocky

Fixed in:0:128.11.0-1.el10_0RHSA-2025:8608

Fixed in:0:128.11.0-1.el8_2RHSA-2025:8631

Fixed in:0:128.11.0-1.el8_4RHSA-2025:8630

Fixed in:0:128.11.0-1.el8_8RHSA-2025:8628

Fixed in:0:128.11.0-1.el8_6RHSA-2025:8629

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8756

Fixed in:0:128.11.0-1.el8_6RHSA-2025:8629

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8756

Fixed in:0:128.11.0-1.el9_0RHSA-2025:8598

Fixed in:0:128.11.0-1.el9_2RHSA-2025:8642

Fixed in:0:128.11.0-1.el9_4RHSA-2025:8599

Fixed in:0:128.11.0-1.el9_2RHSA-2025:8642

Fixed in:0:128.11.0-1.el9_4RHSA-2025:8599

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8607

thunderbird-debugsourceRocky

Fixed in:0:128.11.0-1.el10_0RHSA-2025:8608

Fixed in:0:128.11.0-1.el8_6RHSA-2025:8629

Fixed in:0:128.11.0-1.el8_8RHSA-2025:8628

Fixed in:0:128.11.0-1.el8_6RHSA-2025:8629

Fixed in:0:128.11.0-1.el8_2RHSA-2025:8631

Fixed in:0:128.11.0-1.el8_4RHSA-2025:8630

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8756

Fixed in:0:128.11.0-1.el8_6RHSA-2025:8629

Fixed in:0:128.11.0-1.el8_8RHSA-2025:8628

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8756

Fixed in:0:128.11.0-1.el8_6RHSA-2025:8629

Fixed in:0:128.11.0-1.el9_4RHSA-2025:8599

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8607

Fixed in:0:128.11.0-1.el9_2RHSA-2025:8642

Fixed in:0:128.11.0-1.el9_4RHSA-2025:8599

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8607

Fixed in:0:128.11.0-1.el9_0RHSA-2025:8598

Fixed in:0:128.11.0-1.el9_4RHSA-2025:8599

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8607

Fixed in:0:128.11.0-1.el9_2RHSA-2025:8642

Fixed in:0:128.11.0-1.el9_4RHSA-2025:8599

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8607

Fixed in:0:128.11.0-1.el9_2RHSA-2025:8642

thunderbird-debugsourceRed Hat / RHEL

Fixed in:0:128.11.0-1.el10_0RHSA-2025:8608

Fixed in:0:128.11.0-1.el8_6RHSA-2025:8629

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8756

Fixed in:0:128.11.0-1.el8_6RHSA-2025:8629

Fixed in:0:128.11.0-1.el8_8RHSA-2025:8628

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8756

Fixed in:0:128.11.0-1.el8_2RHSA-2025:8631

Fixed in:0:128.11.0-1.el8_4RHSA-2025:8630

Fixed in:0:128.11.0-1.el8_6RHSA-2025:8629

Fixed in:0:128.11.0-1.el8_10RHSA-2025:8756

Fixed in:0:128.11.0-1.el9_0RHSA-2025:8598

Fixed in:0:128.11.0-1.el9_2RHSA-2025:8642

Fixed in:0:128.11.0-1.el9_4RHSA-2025:8599

Fixed in:0:128.11.0-1.el9_2RHSA-2025:8642

Fixed in:0:128.11.0-1.el9_4RHSA-2025:8599

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8607

Fixed in:0:128.11.0-1.el9_4RHSA-2025:8599

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8607

Fixed in:0:128.11.0-1.el9_0RHSA-2025:8598

Fixed in:0:128.11.0-1.el9_6RHSA-2025:8607

Fixed in:0:128.11.0-1.el9_0RHSA-2025:8598

thunderbirdUbuntu

Fixed in:1:128.12.0+build1-0ubuntu0.22.04.1USN-7663-1

DeveloperEditionWindows application

Affected:128.11.0Fixed in:128.11.0Mozilla

Affected:139.0Fixed in:139.0Mozilla

Mozilla Firefox (en-US)Windows application

Affected:128.11.0Fixed in:128.11.0Mozilla

Affected:139.0Fixed in:139.0Mozilla

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionRequired

ScopeUnchanged

Impact

ConfidentialityLow

IntegrityNone

AvailabilityNone

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

Exploit Intelligence

0.26%probability of exploitation in 30 days

18thpercentile

Low risk: more likely to be exploited than 18% of all known CVEs.

References

Vendor Advisory2

Other references5

Related Vulnerabilities

Other CWE-200 (Information Exposure) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2024-24919	High	8.6	100%	KEV + Ransom	-
CVE-2020-14181	Medium	5.3	100%	-	Fix
CVE-2021-34429	Medium	5.3	99%	-	Fix
CVE-2018-11409	Medium	5.3	98%	-	-
CVE-2021-41277	Critical	10.0	97%	KEV	-
CVE-2016-2183	High	7.5	96%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-13.