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Vulnerability record · CVE-2026-53899 · published 16 June 2026

CVE-2026-53899: Mozilla firefox mobile insufficient verification of data authenticity vulnerability

Mozilla · Firefox Mobile

Firefox for iOS used partial domain matching when attaching cookies to PDF requests, allowing a malicious site on a suffix domain to receive cookies belonging to the target site. This vulnerability was fixed in Firefox for iOS 152.0.

6.5 CVSS 3.1 Medium EPSS 0.14% · top 97.5% CWE-345 · Insufficient verification of data authenticity
6.5CVSS 3.1 base score
0.14%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References
17 Jun 2026Last modified by NVD

Description

Firefox for iOS used partial domain matching when attaching cookies to PDF requests, allowing a malicious site on a suffix domain to receive cookies belonging to the target site. This vulnerability was fixed in Firefox for iOS 152.0.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://bugzilla.mozilla.org/show_bug.cgi?id=2042909 Permissions Required
https://www.mozilla.org/security/advisories/mfsa2026-56/ Vendor Advisory

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-53899), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.