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CVE Record

CVE-2021-39246: Tor Browser through 10.5.6 and 11.x through 11.0a4 allows a correlation attack that can compromise the priv...

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).

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This issue weakens privacy for users who visited v2 onion services with affected Tor Browser versions. The browser could locally record exact visit timestamps, which could be correlated with timestamps from an onion site or rogue Tor-network destination to identify likely visits.

Executive priority

Prioritize this for teams whose safety, legal work, research, or investigations depended on Tor anonymity. For general enterprise desktops, urgency is lower but still warrants cleanup of obsolete Tor Browser versions and sensitive local logs.

Technical view

CVE-2021-39246 affects Tor Browser through 10.5.6 and 11.x through 11.0a4. The recorded local timestamps for v2 onion-service visits create a correlation risk when compared with server-side or rogue-site timing data. Sources do not provide CVSS, CWE, or confirmed active exploitation.

Likely exposure

Exposure is likely limited to users of the named Tor Browser versions who accessed v2 onion addresses. Business impact is highest where user anonymity, source protection, investigations, or sensitive research depended on Tor privacy during that period.

Exploitation context

The bundle does not show CISA KEV listing or confirmed active exploitation. The described attack is a privacy correlation scenario, not a conventional remote code execution issue. It depends on timing evidence from local logs and destination-side or rogue-site observations.

Researcher notes

The provided CVE data lacks CVSS, CWE, CPE, and detailed vendor advisory context. Analysis should remain scoped to v2 onion visits, local timestamp logging, and correlation risk. Do not infer broader Tor Browser compromise or active exploitation from this bundle.

Mitigation direction

  • Identify and retire Tor Browser versions through 10.5.6 and 11.x through 11.0a4.
  • Check Tor Project guidance and use a version containing the referenced fix.
  • Avoid v2 onion-service activity on affected versions.
  • Treat affected local logs as sensitive privacy evidence.
  • Review privacy incident procedures for high-risk users.

Validation and detection

  • Inventory Tor Browser versions used during the affected period.
  • Determine whether users accessed v2 onion addresses from affected versions.
  • Review endpoint log retention for exact onion-service visit timestamps.
  • Confirm deployed Tor packages include the referenced Tor Project commit or later guidance.
  • Assess whether destination-side timestamp data could exist for sensitive activity.
Prepared
Confidence
medium
Sources
7

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2021-39246 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
6Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.