CVE-2021-20728Network attack vector

Phishing via unrestricted custom URL scheme

Published Jun 9, 2021 · Updated Aug 3, 2024

Improper access control in goo blog App allows remote attackers to open arbitrary websites through a custom URL scheme. The Android 1.2.25 and earlier and iOS 1.3.3 and earlier clients accept scheme requests from any app and invoke the URL-opening function without restricting the caller. Exploitation requires user interaction with an attacker-supplied request and can expose the user to a phishing site within the app context.

CVSS severity4.3
Medium
EPSS probability0.99%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper access control in goo blog App allows remote attackers to open arbitrary websites through a custom URL scheme. The Android 1.2.25 and earlier and iOS 1.3.3 and earlier clients accept scheme requests from any app and invoke the URL-opening function without restricting the caller. Exploitation requires user interaction with an attacker-supplied request and can expose the user to a phishing site within the app context.

The record

CVE
CVE-2021-20728
Published
Jun 9, 2021
Updated
Aug 3, 2024
Vendor
NTT Resonant Incorporated
Product
goo blog
Classifications
CWE-284, T1204.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 9, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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=goo blog App for Android ver.1.2.25 and earlier, and goo blog App for iOS ver.1.3.3 and earlier

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

NTT Resonant Incorporated · goo blogversion=goo blog App for Android ver.1.2.25 and earlier, and goo blog App for iOS ver.1.3.3 and earlier

Published CVSS scores

4.3JPCERT/CCAV:N/AC:M/Au:N/C:N/I:P/A:N
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
4.3JPCERT/CCCVSS:3.0/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-284Improper Access Control
T1204.001Malicious Link

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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