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CVE-2021-21323

Regression in DNS leakage from Tor windows

MEDIUM
5.3
CVSS Score
Published: February 23, 2021 at 10:45 PM UTC
Updated: June 17, 2026 at 03:35 AM UTC
1 product affected across 1 vendorBrave

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Severity
MEDIUM5.3
Exploit prediction
EPSS 2%

Description

Brave is an open source web browser with a focus on privacy and security. In Brave versions 1.17.73-1.20.103, the CNAME adblocking feature added in Brave 1.17.73 accidentally initiated DNS requests that bypassed the Brave Tor proxy. Users with adblocking enabled would leak DNS requests from Tor windows to their DNS provider. (DNS requests that were not initiated by CNAME adblocking would go through Tor as expected.) This is fixed in Brave version 1.20.108

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Brave· Bravewordpress-plugin
95%
v < 1.20.1081.17.73 ≤ v ≤ 1.20.103
Affected range stops below 1.20.108, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (5)

x_refsource_MISCPatchThird Party Advisory
Source: [email protected]
https://github.com/brave/brave-browser/issues/13527
x_refsource_CONFIRMThird Party Advisory
Source: [email protected]
https://github.com/brave/brave-browser/security/advisories/GHSA-mqjf-9x5g-2rv6
x_refsource_MISCPatchThird Party Advisory
Source: [email protected]
https://github.com/brave/brave-core/commit/12fe321eaad8acc1cbd1d70b4128f687777bcf15
x_refsource_MISCPatchThird Party Advisory
Source: [email protected]
https://github.com/brave/brave-core/pull/7769
x_refsource_MISCPermissions RequiredThird Party Advisory
Source: [email protected]
https://hackerone.com/reports/1077022

CVSS

5.3MEDIUM[email protected]
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
LOW
Integrity
NONE
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-200

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