CVE-2025-5266

MEDIUMNVD 4.36.5▲

4.3

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.

CVSS v3: 4.3
EG Score: 6.5(medium)
EPSS: 17.4%
KEV: Not listed

Published

May 27, 2025

Last Modified

April 13, 2026

References (7)

security@mozillahttps://bugzilla.mozilla.org/show_bug.cgi?id=1965628
security@mozillahttps://www.mozilla.org/security/advisories/mfsa2025-42/
security@mozillahttps://www.mozilla.org/security/advisories/mfsa2025-44/
security@mozillahttps://www.mozilla.org/security/advisories/mfsa2025-45/
security@mozillahttps://www.mozilla.org/security/advisories/mfsa2025-46/
af854a3a-2127-422b-91ae-364da2661108https://lists.debian.org/debian-lts-announce/2025/05/msg00043.html
af854a3a-2127-422b-91ae-364da2661108https://lists.debian.org/debian-lts-announce/2025/05/msg00046.html

Patch Availability(22)

Vendor / Ecosystem	Fixed in / Patch	Released	Source
ubuntu	xul-ext-lightning (1:128.12.0+build1-0ubuntu0.22.04.1) @ jammy	2026-05-21	ubuntu
redhat	firefox-0:128.11.0-1.el8_6	2025-06-17	redhat
redhat	firefox-0:128.11.0-1.el9_4	2025-06-16	redhat
redhat	firefox-0:128.11.0-1.el9_2	2025-06-16	redhat
redhat	firefox-0:128.11.0-1.el8_4	2025-06-16	redhat
redhat	firefox-0:128.11.0-1.el8_2	2025-06-16	redhat
redhat	firefox-0:128.11.0-1.el8_8	2025-06-16	redhat
redhat	firefox-0:128.11.0-1.el9_0	2025-06-16	redhat
redhat	firefox-0:128.11.0-1.el7_9	2025-06-16	redhat
redhat	thunderbird-0:128.11.0-1.el8_10	2025-06-10	redhat
redhat	thunderbird-0:128.11.0-1.el8_6	2025-06-09	redhat
redhat	thunderbird-0:128.11.0-1.el8_8	2025-06-09	redhat
redhat	thunderbird-0:128.11.0-1.el9_2	2025-06-09	redhat
redhat	thunderbird-0:128.11.0-1.el8_2	2025-06-09	redhat
redhat	thunderbird-0:128.11.0-1.el8_4	2025-06-09	redhat
redhat	thunderbird-0:128.11.0-1.el9_4	2025-06-05	redhat
redhat	thunderbird-0:128.11.0-1.el9_0	2025-06-05	redhat
redhat	thunderbird-0:128.11.0-1.el10_0	2025-06-05	redhat
redhat	thunderbird-0:128.11.0-1.el9_6	2025-06-05	redhat
redhat	firefox-0:128.11.0-1.el10_0	2025-06-02	redhat
redhat	firefox-0:128.11.0-1.el9_6	2025-05-29	redhat
redhat	firefox-0:128.11.0-1.el8_10	2025-05-29	redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

CWE-200Exposure of Sensitive Information to an Unauthorized Actor

All Vendor Advisories

(22)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 14× in last 7d / 59× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

2026-06-21 21:42 UTCOSV refresh
2026-06-21 14:56 UTCEPSS rescore
2026-06-21 14:56 UTCEPSS rescore
2026-06-21 01:59 UTCEPSS rescore
2026-06-21 01:59 UTCEPSS rescore
2026-06-19 19:25 UTCEPSS rescore
2026-06-19 19:25 UTCEPSS rescore
2026-06-18 17:52 UTCEPSS rescore
2026-06-18 17:52 UTCEPSS rescore
2026-06-17 17:52 UTCEPSS rescore
2026-06-16 17:52 UTCEPSS rescore
2026-06-15 17:48 UTCEPSS rescore
2026-06-15 17:48 UTCEPSS rescore
2026-06-14 23:18 UTCEPSS rescore
2026-06-13 23:00 UTCEPSS rescore
2026-06-13 23:00 UTCEPSS rescore
2026-06-12 23:11 UTCEPSS rescore
2026-06-11 14:00 UTCEPSS rescore
2026-06-10 22:18 UTCEPSS rescore
2026-06-10 22:18 UTCEPSS rescore
2026-06-10 13:22 UTCEPSS rescore
2026-06-10 13:22 UTCEPSS rescore
2026-06-08 14:16 UTCEPSS rescore
2026-06-08 14:16 UTCEPSS rescore
2026-06-07 15:24 UTCEPSS rescore

Show 51 more

2026-06-07 15:24 UTCEPSS rescore
2026-06-06 13:47 UTCEPSS rescore
2026-06-06 13:47 UTCEPSS rescore
2026-06-05 22:46 UTCEPSS rescore
2026-06-05 22:46 UTCEPSS rescore
2026-06-05 06:10 UTCEPSS rescore
2026-06-05 06:10 UTCEPSS rescore
2026-06-04 13:12 UTCEPSS rescore
2026-06-04 13:12 UTCEPSS rescore
2026-06-03 06:10 UTCOSV refresh
2026-06-02 20:12 UTCEPSS rescore
2026-06-02 20:12 UTCEPSS rescore
2026-06-01 13:51 UTCEPSS rescore
2026-06-01 13:51 UTCEPSS rescore
2026-05-31 22:30 UTCEPSS rescore
2026-05-31 22:30 UTCEPSS rescore
2026-05-31 00:16 UTCEPSS rescore
2026-05-31 00:16 UTCEPSS rescore
2026-05-29 13:44 UTCEPSS rescore
2026-05-28 13:44 UTCEPSS rescore
2026-05-28 13:44 UTCEPSS rescore
2026-05-28 13:44 UTCEPSS rescore
2026-05-28 13:44 UTCEPSS rescore
2026-05-27 13:40 UTCEPSS rescore
2026-05-27 13:40 UTCEPSS rescore
2026-05-27 13:40 UTCEPSS rescore
2026-05-27 13:40 UTCEPSS rescore
2026-05-26 13:44 UTCEPSS rescore
2026-05-26 13:43 UTCEPSS rescore
2026-05-26 13:43 UTCEPSS rescore
2026-05-26 07:18 UTCEPSS rescore
2026-05-26 07:18 UTCEPSS rescore
2026-05-26 07:18 UTCEPSS rescore
2026-05-24 16:57 UTCEPSS rescore
2026-05-22 21:16 UTCEPSS rescore
2026-05-22 21:16 UTCEPSS rescore
2026-05-22 21:16 UTCEPSS rescore
2026-05-21 22:43 UTCEPSS rescore
2026-05-21 13:18 UTCEG score recompute
2026-05-21 13:18 UTCVendor advisory
2026-05-21 13:17 UTCGHSA enrichment
2026-05-20 22:37 UTCEPSS rescore
2026-05-20 22:37 UTCEPSS rescore
2026-05-20 22:37 UTCEPSS rescore
2026-05-20 22:37 UTCEPSS rescore
2026-05-20 22:37 UTCEPSS rescore
2026-05-20 11:21 UTCEPSS rescore
2026-05-20 11:21 UTCEPSS rescore
2026-05-20 11:21 UTCEPSS rescore
2026-05-20 11:21 UTCEPSS rescore
2026-05-18 21:31 UTCEPSS rescore

Frequently asked(5)

What is CVE-2025-5266?

CVE-2025-5266 is a medium vulnerability published on May 27, 2025. 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.

When was CVE-2025-5266 disclosed?

CVE-2025-5266 was first published in the National Vulnerability Database on May 27, 2025, with the most recent update on April 13, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2025-5266 actively exploited?

CVE-2025-5266 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 17.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

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

CVE-2025-5266 has a CVSS v3 base score of 4.3 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 6.5.

How do I remediate CVE-2025-5266?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2025-5266, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2025-5266

Explore →

Is Your Infrastructure Affected by CVE-2025-5266?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs

CVE-2025-5266

Published

Last Modified

References (7)

Patch Availability(22)

Weakness Classification(1)

All Vendor Advisories

Data Freshness Timeline

Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2025-5266?

Same vendor

Same CWE

CVE-2025-5266

📅 Published

🔄 Last Modified

🔗 References (7)

Patch Availability(22)

Weakness Classification(1)

All Vendor Advisories

Data Freshness Timeline

❓ Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2025-5266?

🔗 Related CVEs(same vendor + same CWE)

Same vendor

Same CWE

Published

Last Modified

References (7)

Frequently asked(5)

Related CVEs(same vendor + same CWE)