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CVE-2021-39246

Tor Browser through 10.5.6 and 11.x through 11.0a4 allows a correlation attack that can...

6.1 Medium

Tor Browser through 10.5.6 and 11.x through 11.0a4 allows a correlation attack that can compromise the privacy of visits to v2 onion addresses. Exact timestamps of these onion-service visits are logged locally, and an attacker might be able to compare them to timestamp data collected by the destination server (or collected by a rogue site within the Tor network).

Attack profile

How easy it is to exploit

Attack vector
Physical
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
None

Exploit likelihood

0.47%Down 0.8 points since Sep 25, 2021
90%50%10%1%

What each source reports

NVD Score used 6.1

Tor Browser through 10.5.6 and 11.x through 11.0a4 allows a correlation attack that can compromise the privacy of visits to v2 onion addresses. Exact timestamps of these onion-service visits are logged locally, and an attacker might be able to compare them to timestamp data collected by the destination server (or collected by a rogue site within the Tor network).

Record
CVE-2021-39246
CVSS 3.1
6.1 MediumCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CVSS 2.0
3.6 LowAV:L/AC:L/Au:N/C:P/I:P/A:N
Weakness
CWE-532
Updated
2026-11-02
CVE List No score

Tor Browser through 10.5.6 and 11.x through 11.0a4 allows a correlation attack that can compromise the privacy of visits to v2 onion addresses. Exact timestamps of these onion-service visits are logged locally, and an attacker might be able to compare them to timestamp data collected by the destination server (or collected by a rogue site within the Tor network).

Record
CVE-2021-39246
Updated
2026-11-02
EUVDEUVD-2021-25608 No score

Tor Browser through 10.5.6 and 11.x through 11.0a4 allows a correlation attack that can compromise the privacy of visits to v2 onion addresses. Exact timestamps of these onion-service visits are logged locally, and an attacker might be able to compare them to timestamp data collected by the destination server (or collected by a rogue site within the Tor network).

Record
EUVD-2021-25608
Updated
2026-11-03
GitHub AdvisoriesGHSA-mqmf-5457-4f39 No score

Tor Browser through 10.5.6 and 11.x through 11.0a4 allows a correlation attack that can...

Tor Browser through 10.5.6 and 11.x through 11.0a4 allows a correlation attack that can compromise the privacy of visits to v2 onion addresses. If --log or --verbose is used, exact timestamps of these onion-service visits are logged locally, and an attacker might be able to compare them to timestamp data collected by the destination server (or collected by a rogue site within the Tor network).

Record
GHSA-mqmf-5457-4f39
Weakness
CWE-532
Updated
2026-11-02
OSV 6.1

Tor Browser through 10.5.6 and 11.x through 11.0a4 allows a correlation attack that can compromise the privacy of visits to v2 onion addresses. Exact timestamps of these onion-service visits are logged locally, and an attacker might be able to compare them to timestamp data collected by the destination server (or collected by a rogue site within the Tor network).

Record
CVE-2021-39246
CVSS 3.1
6.1 MediumCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Updated
2026-11-02

Affected products

History

History
RecordedChangedSources
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-39246 is a medium vulnerability (CVSS 6.1) in Torproject Tor Browser, published September 24, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.47%, the 41st percentile. No source names a fixed version.

References

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