CVE-2021-21373

Name: CVE-2021-21373
Creator: NVD / NIST
Published: 2021-03-26T22:15:12.773+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 5.9/10EPSS 1.16%

Last modified Jun 17, 2026

CVE-2021-21373 is a medium-severity vulnerability rated 5.9/10 on the CVSS scale. Nimble is a package manager for the Nim programming language. In Nim release versions before versions 1.2.10 and 1.4.4, "nimble refresh" fetches a list of Nimble packages over HTTPS by default. EPSS estimates a 1.16% chance of exploitation in the next 30 days.

Description

Nimble is a package manager for the Nim programming language. In Nim release versions before versions 1.2.10 and 1.4.4, "nimble refresh" fetches a list of Nimble packages over HTTPS by default. In case of error it falls back to a non-TLS URL http://irclogs.nim-lang.org/packages.json. An attacker able to perform MitM can deliver a modified package list containing malicious software packages. If the packages are installed and used the attack escalates to untrusted code execution.

Metrics

CVSS 3.1

5.9/10

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

EPSS Probability

1.16%

63.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Nim-Lang	Nim	< 1.2.10
Nim-Lang	Nim	>= 1.4.0, < 1.4.4

References

https://consensys.net/diligence/vulnerabilities/nim-insecure-ssl-tls-defaults-remote-code-execution/Exploit, Third Party Advisory
https://github.com/nim-lang/nimble/blob/master/changelog.markdown#0130Release Notes, Third Party Advisory
https://github.com/nim-lang/security/security/advisories/GHSA-8w52-r35x-rgp8Third Party Advisory
https://consensys.net/diligence/vulnerabilities/nim-insecure-ssl-tls-defaults-remote-code-execution/Exploit, Third Party Advisory
https://github.com/nim-lang/nimble/blob/master/changelog.markdown#0130Release Notes, Third Party Advisory
https://github.com/nim-lang/security/security/advisories/GHSA-8w52-r35x-rgp8Third Party Advisory

Timeline

Published: Mar 26, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-21373?

How severe is CVE-2021-21373?

CVE-2021-21373 has a CVSS score of 5.9/10 (MEDIUM severity). The EPSS model estimates a 1.16% probability of exploitation in the next 30 days.

How do I fix CVE-2021-21373?

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-2021-21373?

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

Scan your code now

Source: NVD / NIST