How severe is CVE-2021-39246?

CVE-2021-39246 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over physical access with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2021-39246 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (37th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-39246?

CVE-2021-39246 primarily affects Torproject Tor Browser. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-39246?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-39246 published?

CVE-2021-39246 was published on 2021-09-24 and last updated on 2026-06-17.

CVE-2021-39246

CVE-2021-39246 is a medium-severity vulnerability in Torproject Tor Browser with a CVSS 3.x base score of 6.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-532.

Key facts

Severity: Medium (CVSS 3.x base score 6.1)
CVSS v2: 3.6
EPSS exploit prediction: 0% (37th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-532
Affected product: Torproject Tor Browser
Published: 2021-09-24
Last modified: 2026-06-17

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).

Frequently asked questions

What is CVE-2021-39246?: 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).
How severe is CVE-2021-39246?: CVE-2021-39246 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over physical access with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2021-39246 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (37th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-39246?: CVE-2021-39246 primarily affects Torproject Tor Browser. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-39246?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-39246 published?: CVE-2021-39246 was published on 2021-09-24 and last updated on 2026-06-17.

References

Affected products (3)

cpe:2.3:a:torproject:tor_browser:*:*:*:*:*:*:*:*
cpe:2.3:a:torproject:tor_browser:11.0:alpha2:*:*:*:*:*:*
cpe:2.3:a:torproject:tor_browser:11.0:alpha4:*:*:*:*:*:*

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