CVE-2026-53900

Name: CVE-2026-53900
Creator: NVD / NIST
Published: 2026-06-16T13:16:37.517+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 4.3/10EPSS 0.10%

Last modified Jun 17, 2026

CVE-2026-53900 is a medium-severity vulnerability rated 4.3/10 on the CVSS scale. 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.. EPSS estimates a 0.10% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

4.3/10

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

EPSS Probability

0.10%

1.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Mozilla	Firefox Mobile	< 152.0

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2043204Permissions Required
https://www.mozilla.org/security/advisories/mfsa2026-56/Vendor Advisory

Timeline

Published: Jun 16, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-53900?

How severe is CVE-2026-53900?

CVE-2026-53900 has a CVSS score of 4.3/10 (MEDIUM severity). The EPSS model estimates a 0.10% probability of exploitation in the next 30 days.

How do I fix CVE-2026-53900?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-53900?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST