CVE-2026-53899 | Cross-origin cookies could be leaked when opening a PDF link

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.

Published: 2026-06-16 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-53899 is rated Low Risk (26.4/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.10%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-53899

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-17 — 0.10% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-53899

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 2.5 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2026-53899

GitHub Security Advisory for CVE-2026-53899

GHSA-848m-8qg2-wmrv · Severity: medium — Firefox for iOS used partial domain matching when attaching cookies to PDF requests, allowing a...

OS Trackers for CVE-2026-53899

vendor priority summary link
debian unimportant CVE-2026-53899 unimportant priority: Debian including 1 source packages (firefox), 1 status rows across 1 suites (sid): resolved 1. https://security-tracker.debian.org/tracker/CVE-2026-53899

Affected software / configurations for CVE-2026-53899

Vendor Product Version Raw CPE
mozilla firefox_mobile < 152.0 cpe:2.3:a:mozilla:firefox_mobile:*:*:*:*:*:iphone_os:*:*

References for CVE-2026-53899

cvelogic Threat Intelligence