# CVE-2021-21374

## Summary

- **CVE ID:** CVE-2021-21374
- **Severity:** HIGH
- **CVSS Score:** 8.1 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:L)
- **CWE:** CWE-348, CWE-599, CWE-349
- **Published:** Mar 26, 2021
- **Last Modified:** Mar 13, 2026

## 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 without full verification of the SSL/TLS certificate due to the default setting of httpClient. 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.

## Affected Products

- nim-lang — security (< 1.2.10)
- nim-lang — security (>= 1.4.0, < 1.4.4)

## References

- [CNA](https://consensys.net/diligence/vulnerabilities/nim-insecure-ssl-tls-defaults-remote-code-execution/)
- [CNA](https://github.com/nim-lang/nimble/blob/master/changelog.markdown#0130)
- [CNA](https://github.com/nim-lang/security/security/advisories/GHSA-c2wm-v66h-xhxx)
- [CNA](https://github.com/nim-lang/Nim/pull/16940)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.31%
- **EPSS Percentile:** 54.1

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-11._