Visit correlation via exact timestamp logging
Published Sep 24, 2021 · Updated Aug 4, 2024
Information disclosure in Tor Browser 10.5.6 and 11.x through 11.0a4 allows physically proximate attackers to correlate visits to v2 onion addresses. Tor's connection-edge code emits a warning at the exact time each v2 onion service responds, and the warning timestamp is retained in the browser's local logs by default. Exploitation requires access to those logs and matching timing data from the destination server or a rogue site, exposing visit privacy without altering browser data or availability.
Summary
What happened
Information disclosure in Tor Browser 10.5.6 and 11.x through 11.0a4 allows physically proximate attackers to correlate visits to v2 onion addresses. Tor's connection-edge code emits a warning at the exact time each v2 onion service responds, and the warning timestamp is retained in the browser's local logs by default. Exploitation requires access to those logs and matching timing data from the destination server or a rogue site, exposing visit privacy without altering browser data or availability.
The record
- CVE
- CVE-2021-39246
- Published
- Sep 24, 2021
- Updated
- Aug 4, 2024
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-532, T1005
- Attack vector
- physical
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 24, 2021CVE publishedPublication date reported by the CVE source.
- Aug 4, 2024Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
What conditions does exploitation require?
What is affected?
Affected products and versions are unavailable in this record.
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Tor Browser v2 onion timestamp proof of conceptfunctional · demonstrated
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Technologies
Your stack
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Your stack
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