HOMEVULNERABILITIESCVE-2021-21373
MEDIUM

CVE-2021-21373

CWE-348Published: March 26, 2021· Updated: Jun 17, 2026

5.9
CVSS v3.1

Official 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.

NVD Source

Technical Analysis

CVE-2021-21373 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in full integrity compromise (data manipulation), with a CVSS base score of 5.9.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityHigh
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityNone
IntegrityHigh
AvailabilityNone
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected Vendors & Products

nim-lang1 product(s)
nim
Source: NVD CPE · 1 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

ADVISORYhttps://consensys.net/diligence/vulnerabilities/nim-insecure-ssl-tls-defaults-remote-code-execution/
ADVISORYhttps://github.com/nim-lang/nimble/blob/master/changelog.markdown#0130
ADVISORYhttps://github.com/nim-lang/security/security/advisories/GHSA-8w52-r35x-rgp8
ADVISORYhttps://consensys.net/diligence/vulnerabilities/nim-insecure-ssl-tls-defaults-remote-code-execution/
ADVISORYhttps://github.com/nim-lang/nimble/blob/master/changelog.markdown#0130
ADVISORYhttps://github.com/nim-lang/security/security/advisories/GHSA-8w52-r35x-rgp8

All References (6)

→
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

Quick Facts

CVE IDCVE-2021-21373
CVSS Score5.9 / 10
SeverityMEDIUM
WeaknessCWE-348
CISA KEVNo
Affected1 vendor(s)
PublishedMar 26, 2021

Related CVEs (CWE-348)

CVE-2026-48772
10.0
CVE-2022-31813
9.8
CVE-2026-58122
9.1
CVE-2026-12249
9.0
CVE-2025-69240
8.8
CVE-2024-27773
8.8

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-21373 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.
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