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Fencer Vulns
high 7.5

CVE-2019-8955 json

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 T…

published 2019-02-21 7 y ago modified 2026-06-17 4 mo ago also EUVD-2019-18342

cvss
7.5
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
4.6%
EPSS 4.6% chance of exploitation in 30 days, percentile 91%
public exploits
0
none known

Summary

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.

Patch / fix

  • torproject tor 0.3.3.12, 0.3.4.11
  • tor Debian 14, Debian 13, Debian 12 0.3.5.8-1

debian advisories DEBIAN-CVE-2019-8955

  • tor Ubuntu Pro 18.04 LTS 0.3.2.10-1ubuntu0.2~esm1

ubuntu advisories UBUNTU-CVE-2019-8955

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • tor openSUSE Tumbleweed 0.4.6.7-2.2
  • tor Package Hub 15, Package Hub 12, openSUSE Leap 15.0 0.3.4.11-bp150.3.6.1

opensuse advisories openSUSE-SU-2024:11469-1openSUSE-SU-2019:1107-1

  • tor Alpine 3.24, Alpine 3.23, Alpine 3.22 +12 more 0.3.5.8-r0
  • tor Alpine 3.8 0.3.3.12-r0
  • tor Alpine 3.9 0.3.4.11-r0

alpine advisories ALPINE-CVE-2019-8955

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2019-8955 updated cvss 4.3

tor: memory exhaustion in the KIST cell scheduler resulting in denial of service

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

4.57% chance of exploitation in the next 30 days, higher than 91% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.0 7.5 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P

Classification

Weakness
  • CWE-770 Allocation of Resources Without Limits or Throttling

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.