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CVE-2021-39246

22
FAUCET Score

CVE-2021-39246 affects Tor Browser versions through 10.5.6 and 11.x through 11.0a4 on Apple, Linux, and Microsoft platforms. This vulnerability allows a correlation attack where an attacker can compromise the privacy of v2 onion address visits by comparing locally logged exact timestamps with data collected by a destination server or rogue Tor network site. Rated as Medium severity (CVSS 6.1), the attack requires physical access (AV:P) but is low complexity (AC:L) and can lead to high confidentiality and integrity impacts (C:H/I:H). There is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or KEV listing, though it has received minimal community discussion.

Impacted Technologies

VendorProductVersion(s)CPE
<= 10.5.6CPE matchmatch criteria
cpe:2.3:a:torproject:tor_browser:*:*:*:*:*:*:*:*
11.0CPE matchmatch criteria
cpe:2.3:a:torproject:tor_browser:11.0:alpha2:*:*:*:*:*:*
11.0CPE matchmatch criteria
cpe:2.3:a:torproject:tor_browser:11.0:alpha4:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.1MEDIUM

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

Attack Vector
PHYSICAL
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
NONE
Exploitability Score
0.9
Impact Score
5.2
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.47%
Probability of exploitation in next 30 days
EPSS Percentile
38.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0047 is in the 75th percentile among its peer group of 1,531 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.2 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

github.com / sickcodes/security/blob/master/advisories/SICK-2021-111.md
ExploitThird Party Advisory
gitlab.torproject.org / tpo/core/tor/-/commit/80c404c4b79f3bcba3fc4585d4c62a62a04f3ed9
PatchVendor Advisory
gitlab.torproject.org / tpo/core/tor/-/merge_requests/434
Vendor Advisory
sick.codes / sick-2021-111
ExploitThird Party Advisory
privacyaffairs.com / cve-2021-39246-tor-vulnerability
Third Party Advisory