CVE-2021-44751Network attack vector

Unwanted calls via unblocked USSD dialer launch

Published Mar 25, 2022 · Updated Aug 4, 2024

USSD handling in F-Secure SAFE Browser for Android 18.5 and earlier allows remote attackers to trigger calls from crafted sites. The browser passes USSD-bearing content from JavaScript or an iframe to the Android dialer without blocking the external action. Visiting a malicious site is required; modern Android dialers require user interaction, while some older releases can place unwanted calls or send USSD messages without it.

CVSS severity4.3
Medium
EPSS probability0.57%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

USSD handling in F-Secure SAFE Browser for Android 18.5 and earlier allows remote attackers to trigger calls from crafted sites. The browser passes USSD-bearing content from JavaScript or an iframe to the Android dialer without blocking the external action. Visiting a malicious site is required; modern Android dialers require user interaction, while some older releases can place unwanted calls or send USSD messages without it.

The record

CVE
CVE-2021-44751
Published
Mar 25, 2022
Updated
Aug 4, 2024
Vendor
F-Secure
Product
F-Secure SAFE Browser for Android
Classifications
CWE-276, T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 25, 2022CVE 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=18.5 <18.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

F-Secure · F-Secure SAFE Browser for Androidversion=18.5 <18.6

Published CVSS scores

4.3F-SecureCVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:L/I:L/A:L
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:P/A:N
5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-276Incorrect Default Permissions
T1189Drive-by Compromise

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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