CVE-2015-2689

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 2.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2020-01-24 · updated 2026-06-17
Weakness: CWE-20

Description

Tor before 0.2.4.26 and 0.2.5.x before 0.2.5.11 does not properly handle pending-connection resolve states during periods of high DNS load, which allows remote attackers to cause a denial of service (assertion failure and daemon exit) via crafted packets.

Affected products

torproject Tor: before 0.2.4.26; from 0.2.5.1 before 0.2.5.11 — fixed in 0.2.4.26, 0.2.5.11

How to fix

Upgrade to a fixed version: torproject Tor 0.2.4.26, 0.2.5.11. Check the vendor advisory for mitigations.

References

https://lists.torproject.org/pipermail/tor-talk/2015-March/037281.html
https://trac.torproject.org/projects/tor/ticket/14129
https://lists.torproject.org/pipermail/tor-talk/2015-March/037281.html
https://trac.torproject.org/projects/tor/ticket/14129

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