---
id: "CVE-2026-109434"
kind: "vulnerability"
aliases: ["CVE-2026-109434"]
title: "Fenrir Sleipnir Android browser: fullscreen mode lets sites fake the address bar"
severity: "medium"
cvss: 5.1
epss: null
exploited: false
status: "open"
category: "other"
products: []
ecosystems: []
tags: ["android", "mobile-browser", "other", "sleipnir"]
not_affected_if: ["version-3.9.0-or-later"]
published_at: "2026-10-19T19:17:19+00:00"
first_seen_at: "2026-10-23T21:57:18+00:00"
updated_at: "2026-10-25T04:29:07+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-109434", "first_seen_at": "2026-10-23T21:57:18+00:00"}]
---

# Fenrir Sleipnir Android browser: fullscreen mode lets sites fake the address bar

Fenrir Sleipnir Browser for Android before 3.9.0 lets a remote page enter fullscreen without showing a persistent indicator, so it can draw a counterfeit address bar showing a trusted domain. An attacker can use that fake bar to harvest credentials or push malware through fake login, update, or payment pages after one user tap.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Open the Sleipnir app and check its version under the app's settings or About screen; compare against `3.9.0`
- unknown

## Fix

- Update Sleipnir Browser for Android to `3.9.0` or later
- unknown

## Timeline

- 2026-10-23T21:57:18+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-109434

## From the sources

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.

---

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