CVE-2021-39246

Name: CVE-2021-39246
Creator: NVD / NIST
Published: 2021-09-24T19:15:07.147+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.1/10EPSS 0.46%

Last modified Jun 17, 2026

CVE-2021-39246 is a medium-severity vulnerability rated 6.1/10 on the CVSS scale. 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).. EPSS estimates a 0.46% chance of exploitation in the next 30 days.

Description

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).

Metrics

CVSS 3.1

6.1/10

CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS Probability

0.46%

36.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-532

Affected Software

Vendor	Product	Versions	Update
Torproject	Tor Browser	<= 10.5.6	—
Torproject	Tor Browser	11.0	Alpha2

References

https://github.com/sickcodes/security/blob/master/advisories/SICK-2021-111.mdExploit, Third Party Advisory
https://gitlab.torproject.org/tpo/core/tor/-/commit/80c404c4b79f3bcba3fc4585d4c62a62a04f3ed9Patch, Vendor Advisory
https://gitlab.torproject.org/tpo/core/tor/-/merge_requests/434Vendor Advisory
https://sick.codes/sick-2021-111Exploit, Third Party Advisory
https://www.privacyaffairs.com/cve-2021-39246-tor-vulnerabilityThird Party Advisory
https://github.com/sickcodes/security/blob/master/advisories/SICK-2021-111.mdExploit, Third Party Advisory
https://gitlab.torproject.org/tpo/core/tor/-/commit/80c404c4b79f3bcba3fc4585d4c62a62a04f3ed9Patch, Vendor Advisory
https://gitlab.torproject.org/tpo/core/tor/-/merge_requests/434Vendor Advisory
https://sick.codes/sick-2021-111Exploit, Third Party Advisory
https://www.privacyaffairs.com/cve-2021-39246-tor-vulnerabilityThird Party Advisory

Timeline

Published: Sep 24, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-39246?

How severe is CVE-2021-39246?

CVE-2021-39246 has a CVSS score of 6.1/10 (MEDIUM severity). The EPSS model estimates a 0.46% probability of exploitation in the next 30 days.

How do I fix CVE-2021-39246?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-39246?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST