What’s Vulnerable › Vulnerabilities

CVE-2009-0654

• Severity: medium (CVSS 5.1 v2.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.4% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2009-02-20 · updated 2026-06-16

Description

Tor 0.2.0.28, and probably 0.2.0.34 and earlier, allows remote attackers, with control of an entry router and an exit router, to confirm that a sender and receiver are communicating via vectors involving (1) replaying, (2) modifying, (3) inserting, or (4) deleting a single cell, and then observing cell recognition errors at the exit router. NOTE: the vendor disputes the significance of this issue, noting that the product's design "accepted end-to-end correlation as an attack that is too expensive to solve."

Affected products

• Tor: through 0.2.0.34; 0.2.0.1-alpha, 0.2.0.2-alpha, 0.2.0.3-alpha, 0.2.0.4-alpha, 0.2.0.5-alpha, 0.2.0.6-alpha (+26)

References

• http://blog.torproject.org/blog/one-cell-enough
• http://www.blackhat.com/html/bh-dc-09/bh-dc-09-archives.html#Fu
• http://www.blackhat.com/presentations/bh-dc-09/Fu/BlackHat-DC-09-Fu-Break-Tors-Anonymity.pdf
• http://blog.torproject.org/blog/one-cell-enough
• http://www.blackhat.com/html/bh-dc-09/bh-dc-09-archives.html#Fu
• http://www.blackhat.com/presentations/bh-dc-09/Fu/BlackHat-DC-09-Fu-Break-Tors-Anonymity.pdf

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