CVE-2021-0341Network attack vector

Remote information disclosure via Unicode hostname collisions

Published Feb 10, 2021 · Updated Aug 3, 2024

Improper certificate validation in Android 8.1 through 11 allows remote attackers to disclose network data via a spoofed TLS certificate. OkHostnameVerifier.verifyHostName lowercases untrusted non-ASCII hostnames and certificate SANs, allowing Unicode case-folding collisions to match different DNS names. Exploitation requires a trusted certificate containing a colliding non-ASCII name and a network position able to intercept the device's TLS connection.

CVSS severity7.5
High
EPSS probability0.88%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in Android 8.1 through 11 allows remote attackers to disclose network data via a spoofed TLS certificate. OkHostnameVerifier.verifyHostName lowercases untrusted non-ASCII hostnames and certificate SANs, allowing Unicode case-folding collisions to match different DNS names. Exploitation requires a trusted certificate containing a colliding non-ASCII name and a network position able to intercept the device's TLS connection.

The record

CVE
CVE-2021-0341
Published
Feb 10, 2021
Updated
Aug 3, 2024
Vendor
Google Cloud
Product
Android
Classifications
CWE-295, T1638
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 10, 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=Android-8.1 Android-9 Android-10 Android-11

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Google Cloud · Androidversion=Android-8.1 Android-9 Android-10 Android-11

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
5.0NIST NVDAV:N/AC:L/Au:N/C:P/I:N/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-295Improper Certificate Validation
T1638Adversary-in-the-Middle

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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