CVE-2021-28089

Name: CVE-2021-28089
Creator: NVD / NIST
Published: 2021-03-19T05:15:12.807+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 1.67%

Last modified Jun 17, 2026

CVE-2021-28089 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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.. EPSS estimates a 1.67% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

1.67%

73.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-400

Affected Software

Vendor	Product	Versions	Update
Torproject	Tor	< 0.3.5.14	—
Torproject	Tor	>= 0.4.4.4, < 0.4.4.8	—
Torproject	Tor	>= 0.4.5.0, < 0.4.5.7	—
Torproject	Tor	0.4.4.0	Alpha
Torproject	Tor	0.4.4.1	Alpha
Torproject	Tor	0.4.4.2	Alpha
Torproject	Tor	0.4.4.3	Alpha
Fedoraproject	Fedora	33	—

References

https://blog.torproject.org/node/2009Release Notes, Vendor Advisory
https://gitlab.torproject.org/tpo/core/tor/-/issues/40304Vendor Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HPDXB2GZHG3VNOTWSXQ3QZVHNV76WCU5/
https://security.gentoo.org/glsa/202107-25Third Party Advisory
https://blog.torproject.org/node/2009Release Notes, Vendor Advisory
https://gitlab.torproject.org/tpo/core/tor/-/issues/40304Vendor Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HPDXB2GZHG3VNOTWSXQ3QZVHNV76WCU5/
https://security.gentoo.org/glsa/202107-25Third Party Advisory

Timeline

Published: Mar 19, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-28089?

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.

How severe is CVE-2021-28089?

CVE-2021-28089 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 1.67% probability of exploitation in the next 30 days.

How do I fix CVE-2021-28089?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-28089?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST