CVE-2026-109434

Fenrir Sleipnir Browser for Android before 3.9.0 contains a UI spoofing vulnerability that allows remote attackers to impersonate the browser's trusted address bar by entering fullscreen mode via the Fullscreen API without displaying a persistent notification or trusted-origin indicator. Attackers can render a counterfeit address bar showing a trusted origin over attacker-controlled content after a single user tap, enabling credential harvesting, malware delivery, or social engineering through fake login, update, or payment pages.

CVSS 4.0

5.1CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

CVSS 3.1

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

EPSS

0.3% chance of exploitation in the next 30 days; higher than 22% of CVEs (scores of 2026-10-25)

CWE

CWE-451

Published

2026-10-19

Modified

2026-10-19

Record from

the NVD, synced 2026-10-21

References

• https://www.fenrir-inc.com/jp/news/2026/10/15/sleipnir-mobile-for-android-3-9-0/
• https://www.vulncheck.com/advisories/sleipnir-browser-fullscreen-address-bar-spoofing

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