CVE-2021-20747Network attack vector

Phishing via unauthorized custom URL navigation

Published Jul 14, 2021 · Updated Aug 3, 2024

Improper authorization in Retty App for Android before 4.8.13 and iOS before 4.11.14 allows remote attackers to open arbitrary sites. Its custom URL scheme handler launches the app and follows an attacker-supplied URL without adequately authorizing the destination. Exploitation requires a user to activate the crafted link, after which the app can present an attacker-chosen site for phishing; no data modification or service interruption is reported.

CVSS severity4.3
Medium
EPSS probability1.00%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper authorization in Retty App for Android before 4.8.13 and iOS before 4.11.14 allows remote attackers to open arbitrary sites. Its custom URL scheme handler launches the app and follows an attacker-supplied URL without adequately authorizing the destination. Exploitation requires a user to activate the crafted link, after which the app can present an attacker-chosen site for phishing; no data modification or service interruption is reported.

The record

CVE
CVE-2021-20747
Published
Jul 14, 2021
Updated
Aug 3, 2024
Vendor
Retty Inc.
Product
Retty
Classifications
CWE-939, CWE-862, T1204.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 14, 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=Retty App for Android versions prior to 4.8.13 and Retty App for iOS versions prior to 4.11.14

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Retty Inc. · Rettyversion=Retty App for Android versions prior to 4.8.13 and Retty App for iOS versions prior to 4.11.14

Published CVSS scores

4.3JVNAV:N/AC:M/Au:N/C:N/I:P/A:N
4.3NVDAV:N/AC:M/Au:N/C:P/I:N/A:N
4.3NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
4.3JVNCVSS: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-939Improper Authorization in Handler for Custom URL Scheme
CWE-862Missing Authorization
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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