CVE-2021-22917Network attack vector

DNS query disclosure via Tor proxy bypass

Published Jul 12, 2021 · Updated Aug 3, 2024

Information disclosure in Brave Browser Desktop 1.17 through 1.20 allows remote attackers to expose DNS queries from Tor windows. CNAME ad blocking initiates system DNS requests instead of sending them through the Tor proxy. Exposure requires enabled ad blocking and a Tor-window navigation that triggers CNAME uncloaking; the DNS provider learns the queried name and source IP.

CVSS severity6.5
Medium
EPSS probability1.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in Brave Browser Desktop 1.17 through 1.20 allows remote attackers to expose DNS queries from Tor windows. CNAME ad blocking initiates system DNS requests instead of sending them through the Tor proxy. Exposure requires enabled ad blocking and a Tor-window navigation that triggers CNAME uncloaking; the DNS provider learns the queried name and source IP.

The record

CVE
CVE-2021-22917
Published
Jul 12, 2021
Updated
Aug 3, 2024
Vendor
Brave Software, Inc.
Product
Brave Browser
Classifications
CWE-200
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 12, 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=Fixed in 1.20

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Brave Software, Inc. · Brave Browserversion=Fixed in 1.20

Published CVSS scores

4.3NISTAV:N/AC:M/Au:N/C:P/I:N/A:N
6.5NISTCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/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 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-200Exposure of Sensitive Information to an Unauthorized Actor

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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