Tor 0.2.0.28, and probably 0.2.0.34 and earlier, allows remote attackers,...

Vulnerability 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."

References

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