SB2026072296 - Multiple vulnerabilities in Firefox for iOS

Description

This security bulletin contains information about 2 vulnerabilities.

1) Input validation error (CVE-ID: CVE-2026-53899)

CWE-ID: CWE-20 - Improper input validation

CVSSv4: 6.7 [CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]

The vulnerability allows a remote attacker to disclose sensitive information.

The vulnerability exists due to improper cookie domain validation in PDF requests when opening a PDF link. A remote attacker can host a malicious site on a suffix domain to disclose sensitive information.

2) Interpretation Conflict (CVE-ID: CVE-2026-53900)

CWE-ID: CWE-436 - Interpretation Conflict

CVSSv4: 6.7 [CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N]

The vulnerability allows a remote attacker to inject arbitrary cookies into requests to an unrelated target domain.

The vulnerability exists due to improper cookie handling in TemporaryDocument when opening a PDF link that triggers cross-origin HTTP redirects. A remote attacker can cause cross-origin redirects from the initial PDF request to inject arbitrary cookies into requests to an unrelated target domain.

Remediation

Install update from vendor's website.

References

• https://www.mozilla.org/en-US/security/advisories/mfsa2026-56/
• https://bugzilla.mozilla.org/show_bug.cgi?id=2042909
• https://bugzilla.mozilla.org/show_bug.cgi?id=2043204