Security readout for executives and security teams
Plain-English summary
Nim applications using the standard httpClient before version 1.4.2 could make HTTPS requests without checking that the server certificate is trustworthy. A network attacker could impersonate or alter a connection, putting data integrity at risk when affected code relies on default settings.
Executive priority
Treat this as a targeted remediation item for Nim-based systems, especially internal automation or services making trusted HTTPS calls. It is not reported as actively exploited, but it can undermine trust in encrypted connections.
Technical view
CVE-2021-29495 is a CWE-295 certificate validation flaw in Nim standard library httpClient before 1.4.2. SSL/TLS peer certificate verification was disabled by default. The CVSS 3.1 score is 5.9, with network attack vector, high attack complexity, no privileges, no user interaction, and high integrity impact.
Likely exposure
Exposure is most likely in Nim services, tools, or scripts built with Nim standard library versions before 1.4.2 that use httpClient for HTTPS and did not explicitly enable peer verification.
Exploitation context
The source bundle does not report active exploitation, and KEV status is false. Practical exploitation would require a suitable network interception position and an affected client using insecure default TLS verification behavior.
Researcher notes
Focus review on Nim stdlib httpClient before 1.4.2 and TLS client configuration. The available sources identify the vulnerable default and workaround, but do not provide evidence of exploitation in the wild or additional affected products.
Mitigation direction
- Upgrade Nim to version 1.4.2 or later where feasible.
- As a documented workaround, set verifyMode = CVerifyPeer.
- Audit Nim applications for stdlib httpClient HTTPS usage with default SSL settings.
- Check the Nim advisory for any current vendor guidance.
Validation and detection
- Inventory Nim compiler and standard library versions in affected projects.
- Review code for httpClient usage without explicit peer certificate verification.
- Confirm builds are using Nim 1.4.2 or later.
- Test HTTPS client behavior rejects invalid or untrusted certificates.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-295: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-29495 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 5.9 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N2.23.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.9MediumVector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/nim-lang/security/security/advisories/GHSA-9vqv-2jj9-7mqrCVE reference · x_refsource_CONFIRM
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Certificate Validation
Improper Certificate Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.