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.
CVE-2021-21374
This high-severity CVE scores 8.1 under NVD CVSS v3. EPSS exploit probability: 0.3%, top 45% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
- High severity, but no confirmed exploitation yet
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 8.1
- EG Score
- 8.1(medium)
- EPSS
- 59.8%
- KEV
- Not listed
Published
March 26, 2021
Last Modified
November 21, 2024
References (8)
- security-advisories@githubhttps://consensys.net/diligence/vulnerabilities/nim-insecure-ssl-tls-defaults-remote-code-execution/
- security-advisories@githubhttps://github.com/nim-lang/Nim/pull/16940
- security-advisories@githubhttps://github.com/nim-lang/nimble/blob/master/changelog.markdown#0130
- security-advisories@githubhttps://github.com/nim-lang/security/security/advisories/GHSA-c2wm-v66h-xhxx
- af854a3a-2127-422b-91ae-364da2661108https://consensys.net/diligence/vulnerabilities/nim-insecure-ssl-tls-defaults-remote-code-execution/
- af854a3a-2127-422b-91ae-364da2661108https://github.com/nim-lang/Nim/pull/16940
- af854a3a-2127-422b-91ae-364da2661108https://github.com/nim-lang/nimble/blob/master/changelog.markdown#0130
- af854a3a-2127-422b-91ae-364da2661108https://github.com/nim-lang/security/security/advisories/GHSA-c2wm-v66h-xhxx
Weakness Classification(4)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 9× in last 7d / 47× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-11 08:25 UTCEPSS rescore
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- 2026-07-01 06:18 UTCOSV refresh
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- 2026-05-26 19:06 UTCEG score recompute
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- 2026-05-26 07:17 UTCEPSS rescore
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- 2026-05-24 16:49 UTCEPSS rescore
Related CVEs(same CWE)
Same CWE
10 shownCWE-295
Frequently asked(5)
What is CVE-2021-21374?
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