Is CVE-2026-53900 in the CISA KEV catalog?

No. CVE-2026-53900 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-53900?

CVE-2026-53900 has a CVSS v3 base score of 4.3 (MEDIUM).

What is the EPSS score for CVE-2026-53900?

CVE-2026-53900 has an EPSS score of 0.10% (1th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-53900?

Upgrade firefox mobile to 152.0 or later.

CVE & CISA-KEV Catalog

CVE-2026-53900

MEDIUM

4.3

CVSS v3

NVD

Description

Firefox for iOS preserved cookies set on the initial PDF request across cross-origin HTTP redirects in TemporaryDocument, allowing a malicious site to inject arbitrary cookies into requests to an unrelated target domain. This vulnerability was fixed in Firefox for iOS 152.0.

CWE-345 CWE-384

How to fix

Remediation Available

firefox mobileNVD

Affected:< 152.0Fixed in:152.0CVE-2026-53900derived 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 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

0.10%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.