CVE-2019-8955

Severity: high (CVSS 7.5 v3.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 4.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2019-02-21 · updated 2026-06-17
Weakness: CWE-770

Description

In Tor before 0.3.3.12, 0.3.4.x before 0.3.4.11, 0.3.5.x before 0.3.5.8, and 0.4.x before 0.4.0.2-alpha, remote denial of service against Tor clients and relays can occur via memory exhaustion in the KIST cell scheduler.

Affected products

torproject Tor: before 0.3.3.12; from 0.3.4.8 before 0.3.4.11; 0.3.4.0-alpha-dev, 0.3.4.1-alpha, 0.3.4.2-alpha, 0.3.4.3-alpha, 0.3.4.4-rc, 0.3.4.5-rc (+11) — fixed in 0.3.3.12, 0.3.4.11

How to fix

Upgrade to a fixed version: torproject Tor 0.3.3.12, 0.3.4.11. Check the vendor advisory for mitigations.

References

http://lists.opensuse.org/opensuse-security-announce/2019-04/msg00013.html
http://www.securityfocus.com/bid/107136
https://blog.torproject.org/new-releases-tor-0402-alpha-0358-03411-and-03312
https://trac.torproject.org/projects/tor/ticket/29168
http://lists.opensuse.org/opensuse-security-announce/2019-04/msg00013.html
http://www.securityfocus.com/bid/107136
https://blog.torproject.org/new-releases-tor-0402-alpha-0358-03411-and-03312
https://trac.torproject.org/projects/tor/ticket/29168

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