CVE-2021-21373: Nimble falls back to insecure http url when fetching packages
Noroxi assessment
Priority: Monitor (action score 23/100)
- The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
- Probability of exploitation in the next 30 days: 1.1% (FIRST EPSS); higher than 67.2% of all records.
- Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
- Fixed version: nim (Debian:12) 1.4.6+really1.4.2-1; nim (openSUSE:Leap 15.2) 1.2.12-lp152.2.3.1; nim (openSUSE:Leap 15.3) 1.6.6-bp153.2.3.1.
Low priority for now. Upgrade to nim (Debian:12) 1.4.6+really1.4.2-1; nim (openSUSE:Leap 15.2) 1.2.12-lp152.2.3.1; nim (openSUSE:Leap 15.3) 1.6.6-bp153.2.3.1 or later.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
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.
- Published
- Mar 26, 2021
- Updated
- Jun 16, 2026
- EPSS
- 1.1% · 67th percentile
- CWE
- CWE-348
Report tools
Action score
23
Monitor
Low priority for now.
- CVSS
- 23 / 40 · 5.9 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 1.1%
CNA vs NVD score
- NVD
- 5.9
- CNA · GitHub_M
- 7.5
- 1.6 point gap
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:H/A:L
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- No public exploit code on record
- A fix has been released
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Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
| Vendor | Product | CPE |
|---|---|---|
| nim-lang | nim | cpe:2.3:a:nim-lang:nim |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- nim-lang nimbefore 1.2.10
- nim-lang nim1.4.0 and later · before 1.4.4
Versions reported by the vendor
Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.
nim-lang security
- < 1.2.10, >= 1.4.0, < 1.4.4affected
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | nim | before 1.4.6+really1.4.2-1 | 1.4.6+really1.4.2-1 |
| openSUSE:Leap 15.2 | nim | before 1.2.12-lp152.2.3.1 | 1.2.12-lp152.2.3.1 |
| openSUSE:Leap 15.3 | nim | before 1.6.6-bp153.2.3.1 | 1.6.6-bp153.2.3.1 |
| openSUSE:Leap 15.4 | nim | before 1.6.6-bp154.2.3.1 | 1.6.6-bp154.2.3.1 |
| openSUSE:Tumbleweed | nim | before 1.2.12-1.7 | 1.2.12-1.7 |
| SUSE:Package Hub 15 SP2 | nim | before 1.2.12-bp152.4.3.1 | 1.2.12-bp152.4.3.1 |
| SUSE:Package Hub 15 SP3 | nim | before 1.6.6-bp153.2.3.1 | 1.6.6-bp153.2.3.1 |
| SUSE:Package Hub 15 SP4 | nim | before 1.6.6-bp154.2.3.1 | 1.6.6-bp154.2.3.1 |
Same product
nim-lang: all recordsOther highest-scoring records for the same primary product.
- CVE-2020-15690In Nim before 1.2.6, the standard library asyncftpclient lacks a check for whether a message contains a newline character.40Plan
- CVE-2020-15692In Nim 1.2.4, the standard library browsers mishandles the URL argument to browsers.openDefaultBrowser.40Plan
- CVE-2021-21372Nimble arbitrary code execution for specially crafted package metadata36Monitor
Published before and after this one in the same product
- ← EarlierCVE-2020-15693Aug 14, 2020 · In Nim 1.2.4, the standard library httpClient is vulnerable to a CR-LF injection in the target URL.27Monitor
- ← EarlierCVE-2020-15694Aug 14, 2020 · In Nim 1.2.4, the standard library httpClient fails to properly validate the server response.31Monitor
- Later →CVE-2021-21374Mar 26, 2021 · Nimble fails to validate certificates due to insecure httpClient defaults32Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| debian:nim | 1.4.6+really1.4.2-1 · Debian:12 | Package registry (OSV) |
| opensuse:nim | 1.2.12-lp152.2.3.1 · openSUSE:Leap 15.2 | Package registry (OSV) |
| opensuse:nim | 1.6.6-bp153.2.3.1 · openSUSE:Leap 15.3 | Package registry (OSV) |
| suse:nim | 1.2.12-bp152.4.3.1 · SUSE:Package Hub 15 SP2 | Package registry (OSV) |
| suse:nim | 1.6.6-bp153.2.3.1 · SUSE:Package Hub 15 SP3 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
No history yet (it accumulates with the daily EPSS job).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- Special conditions such as timing or configuration are required.
If successful
- Confidentiality
- none
- Integrity
- high · data or configuration can be modified
- Availability
- none
- Attack vector
- Network
- Attack complexity
- High
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- None
- Integrity impact
- High
- Availability impact
- None
Weakness class (CWE)
CWE-348 · Use of Less Trusted SourceCVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
nvd-primary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
Change log
- Fix✗ → ✓
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References
Show all references (1 more)Show less
Vendor advisories and official records. Exploit/PoC links are deliberately left out.