How severe is CVE-2021-21374?

CVE-2021-21374 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity high, and availability low.

Is CVE-2021-21374 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (60th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-21374?

CVE-2021-21374 affects Nim-lang Nim. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-21374?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-21374 published?

CVE-2021-21374 was published on 2021-03-26 and last updated on 2026-06-17.

CVE-2021-21374

CVE-2021-21374 is a high-severity vulnerability in Nim-lang Nim with a CVSS 3.x base score of 8.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-295.

Key facts

Severity: High (CVSS 3.x base score 8.1)
CVSS v2: 6.8
EPSS exploit prediction: 1% (60th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-295
Affected product: Nim-lang Nim
Published: 2021-03-26
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2021-21374?: 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.
How severe is CVE-2021-21374?: CVE-2021-21374 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity high, and availability low.
Is CVE-2021-21374 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (60th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-21374?: CVE-2021-21374 affects Nim-lang Nim. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-21374?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-21374 published?: CVE-2021-21374 was published on 2021-03-26 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:nim-lang:nim:*:*:*:*:*:*:*:*

More vulnerabilities in Nim-lang Nim

CVE-2020-15690 — Critical (CVSS 9.8): In Nim before 1.2.6, the standard library asyncftpclient lacks a check for whether a message contains a newline…
CVE-2020-15692 — Critical (CVSS 9.8): In Nim 1.2.4, the standard library browsers mishandles the URL argument to browsers.openDefaultBrowser. This argument…
CVE-2021-21372 — High (CVSS 8.3): Nimble is a package manager for the Nim programming language. In Nim release version before versions 1.2.10 and 1.4.4,…
CVE-2021-21373 — High (CVSS 7.5): Nimble is a package manager for the Nim programming language. In Nim release versions before versions 1.2.10 and 1.4.4,…
CVE-2020-15694 — High (CVSS 7.5): In Nim 1.2.4, the standard library httpClient fails to properly validate the server response. For example,…
CVE-2020-15693 — Medium (CVSS 6.5): In Nim 1.2.4, the standard library httpClient is vulnerable to a CR-LF injection in the target URL. An injection is…

All CVEs affecting Nim-lang Nim →

Other CWE-295 (Improper Certificate Validation) vulnerabilities

CVE-2026-4370 — Critical (CVSS 10.0): A vulnerability was identified in Juju from version 3.2.0 until 3.6.19 and from version 4.0 until 4.0.4, where the…
CVE-2026-30836 — Critical (CVSS 10.0): Step CA is an online certificate authority for secure, automated certificate management for DevOps. Versions 0.30.0-rc6…
CVE-2025-68121 — Critical (CVSS 10.0): During session resumption in crypto/tls, if the underlying Config has its ClientCAs or RootCAs fields mutated between…
CVE-2022-20703 — Critical (CVSS 10.0): Multiple vulnerabilities in Cisco Small Business RV160, RV260, RV340, and RV345 Series Routers could allow an attacker…
CVE-2021-1471 — Critical (CVSS 9.9): Multiple vulnerabilities in Cisco Jabber for Windows, Cisco Jabber for MacOS, and Cisco Jabber for mobile platforms…
CVE-2026-20184 — Critical (CVSS 9.8): A vulnerability in the integration of single sign-on (SSO) with Control Hub in Cisco Webex Services could have allowed…

Browse all CWE-295 (Improper Certificate Validation) vulnerabilities →