Vulnerability · Published Oct 19, 2026 · Assigned by VulnCheck

CVE-2026-109434Sleipnir Browser < 3.9.0 Fullscreen Address Bar Spoofing

Medium 4.3

In plain English

A medium-severity security flaw in Sleipnir Mobile for Android from Fenrir. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 23% of all known vulnerabilities).

Severity (CVSS 3.1)4.3Medium

Exploit odds (30 days)0.3%top 76.9% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

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.

Affected products (as reported)

Vendor	Product	Versions
Fenrir	Sleipnir Mobile for Android	0 – before 3.9.0

Weakness: CWE-451 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

References

Vendor Advisory vendor-advisory, patch
VulnCheck Advisory: Sleipnir Browser < 3.9.0 Fullscreen Address Bar Spoofing third-party-advisory