CVE-2021-40834Network attack vector

Content spoofing via full-screen browser interface hiding

Published Dec 10, 2021 · Updated Aug 4, 2024

UI overlay in SAFE Browser within F-Secure Mobile Security 17.9 and earlier allows remote attackers to spoof content via a crafted URL. Opening the URL makes the embedded browser enter full-screen mode and hide its interface, removing trusted browser chrome that would expose the page's identity. A user must open the crafted URL, and the established consequence is visual impersonation rather than code execution or data access.

CVSS severity4.3
Medium
EPSS probability0.73%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

UI overlay in SAFE Browser within F-Secure Mobile Security 17.9 and earlier allows remote attackers to spoof content via a crafted URL. Opening the URL makes the embedded browser enter full-screen mode and hide its interface, removing trusted browser chrome that would expose the page's identity. A user must open the crafted URL, and the established consequence is visual impersonation rather than code execution or data access.

The record

CVE
CVE-2021-40834
Published
Dec 10, 2021
Updated
Aug 4, 2024
Vendor
F-Secure
Product
F-Secure Mobile Security
Classifications
CWE-1021, T1036
Attack vector
network
Privileges
Unavailable

Timeline

How it unfolded

  1. Dec 10, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=18.5x <17.9*

What conditions does exploitation require?

Attack vectornetwork
Required privilegesUnavailable in this record.

What is affected?

F-Secure · F-Secure Mobile Securityversion=18.5x <17.9*

Published CVSS scores

4.3F-SecureCVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:L/I:L/A:L
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
4.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1021Improper Restriction of Rendered UI Layers or Frames
T1036Masquerading

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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