Vulnerability

CVE-2026-53900

Medium· 4.3CVSS4.3EPSS0%

.rules3/5

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

Threat signal

50/100

Elevated

Severity

medium

CVSS

4.3

EPSS

Active

CVSS

v3.1via NVDOpen in FIRST calculator →

4.3/ 10MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

Attack VectorNetworkExploitable remotely over the internet — no local access needed.
Attack ComplexityLowNo special conditions — exploit works reliably.
Privileges RequiredNoneUnauthenticated — no credentials needed.
User InteractionRequiredRequires user action (click, file open, etc).
ScopeUnchangedImpact contained to the vulnerable component.
Confidentiality ImpactLowSome data disclosure; attacker doesn't fully control what.
Integrity ImpactNoneNo integrity impact.
Availability ImpactNoneNo availability impact.

EPSS

Exploit prediction · 30-day horizonFIRST.org →

0.14%

probability of exploitation in next 30 days

higher than 3% of all CVEs

10-day trend↑ 0pp

Low exploitation likelihood — defer if no other signals fire.

Vendor VEX

No VEX statements published for CVE-2026-53900. Vendors publish VEX (Vulnerability Exploitability eXchange) to assert per-product whether a CVE is actually exploitable in their distribution.

SSVCDefer

No exploitation, limited impact or prevalence

exploitation: none
automatable: no
impact: partial
mission: support

Lifecycle

2026-06-16Published
2026-06-17Last modified1 source

CVE-2026-53900

CVSS

EPSS

Vendor VEX

Lifecycle

References

CVE-2026-53900

CVSS

EPSS

Vendor VEX

Lifecycle

References