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Fencer Vulns
high 7.5

CVE-2021-28089 json

Tor before 0.4.5.7 allows a remote participant in the Tor directory protocol to exhaust CPU resources on a target, aka TROVE-2021-001.

published 2021-03-19 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-14794

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.7%
EPSS 1.7% chance of exploitation in 30 days, percentile 76%
public exploits
0
none known

Summary

Tor before 0.4.5.7 allows a remote participant in the Tor directory protocol to exhaust CPU resources on a target, aka TROVE-2021-001.

Patch / fix

  • torproject tor 0.3.5.14, 0.4.4.8, 0.4.5.7
  • tor Debian 14, Debian 13, Debian 12 0.4.5.7-1

debian advisories DEBIAN-CVE-2021-28089

  • tor Ubuntu Pro 16.04 LTS 0.2.9.14-1ubuntu1~16.04.3+esm1
  • tor Ubuntu Pro 18.04 LTS 0.3.2.10-1ubuntu0.2~esm2
  • tor Ubuntu Pro 20.04 LTS 0.4.2.7-1ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2021-28089

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 SP2 0.4.5.7-bp152.2.9.1
  • tor openSUSE Leap 15.2 0.4.5.7-lp152.2.9.1

opensuse advisories openSUSE-SU-2024:11469-1openSUSE-SU-2021:0474-1openSUSE-SU-2021:0461-1

  • tor Alpine 3.10 0.3.5.14-r0
  • tor Alpine 3.12, Alpine 3.11 0.4.4.9-r0
  • tor Alpine 3.13 0.4.4.8-r0
  • tor Alpine 3.24, Alpine 3.23, Alpine 3.22 +8 more 0.4.5.7-r0

alpine advisories ALPINE-CVE-2021-28089

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

  • tor Arch Linux 0.4.5.7-1

arch linux advisories AVG-1699

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-2021-28089 updated cvss 5.9

tor: dump_desc function was called incorrectly in several places in a way that could lead to excessive CPU usage

  • 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

1.67% chance of exploitation in the next 30 days, higher than 76% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 7.5 CVSS:3.1/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-400 Uncontrolled Resource Consumption

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.