Is CVE-2026-53899 in the CISA KEV catalog?

No. CVE-2026-53899 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-53899?

CVE-2026-53899 has a CVSS v3 base score of 6.5 (MEDIUM).

What is the EPSS score for CVE-2026-53899?

CVE-2026-53899 has an EPSS score of 0.10% (1th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-53899?

Upgrade firefox mobile to 152.0 or later.

CVE & CISA-KEV Catalog

CVE-2026-53899

MEDIUM

6.5

CVSS v3

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.

CWE-345

How to fix

Remediation Available

firefox mobileNVD

Affected:< 152.0Fixed in:152.0CVE-2026-53899derived from NVD

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 InteractionNone

ScopeUnchanged

Impact

ConfidentialityLow

IntegrityLow

AvailabilityNone

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

Exploit Intelligence

0.10%probability of exploitation in 30 days

1stpercentile

Low risk: more likely to be exploited than 1% of all known CVEs.

References

Vendor Advisory1

mozilla.org

Other references1

bugzilla.mozilla.org

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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 2026-06-17.