How severe is CVE-2025-5263?

CVE-2025-5263 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity none, and availability none.

Is CVE-2025-5263 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (12th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-5263?

CVE-2025-5263 primarily affects Mozilla Firefox. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2025-5263?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2025-5263 have an EU (EUVD) identifier?

Yes. CVE-2025-5263 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-18108.

When was CVE-2025-5263 published?

CVE-2025-5263 was published on 2025-05-27 and last updated on 2026-06-17.

CVE-2025-5263

CVE-2025-5263 is a medium-severity vulnerability in Mozilla Firefox with a CVSS 3.x base score of 4.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-346.

Key facts

Severity: Medium (CVSS 3.x base score 4.3)
EPSS exploit prediction: 0% (12th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-18108
Weakness: CWE-346
Affected product: Mozilla Firefox
Published: 2025-05-27
Last modified: 2026-06-17

Description

Error handling for script execution was incorrectly isolated from web content, which could have allowed cross-origin leak attacks. This vulnerability was fixed in Firefox 139, Firefox ESR 115.24, Firefox ESR 128.11, Thunderbird 139, and Thunderbird 128.11.

Frequently asked questions

What is CVE-2025-5263?: Error handling for script execution was incorrectly isolated from web content, which could have allowed cross-origin leak attacks. This vulnerability was fixed in Firefox 139, Firefox ESR 115.24, Firefox ESR 128.11, Thunderbird 139, and Thunderbird 128.11.
How severe is CVE-2025-5263?: CVE-2025-5263 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity none, and availability none.
Is CVE-2025-5263 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (12th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-5263?: CVE-2025-5263 primarily affects Mozilla Firefox. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2025-5263?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-5263 have an EU (EUVD) identifier?: Yes. CVE-2025-5263 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-18108.
When was CVE-2025-5263 published?: CVE-2025-5263 was published on 2025-05-27 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:-:*:*

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