Security readout for executives and security teams
Plain-English summary
CVE-2021-46872 is a cross-site scripting risk in Nim's standard-library RST handling before Nim 1.6.2. Applications that render untrusted RST content could allow a malicious link scheme through. Business urgency is moderate: it can affect users through web content, but the record requires user interaction and does not show known active exploitation.
Executive priority
Treat this as a moderate-priority web content safety issue. Prioritize remediation where public users can submit RST content or where NimForum is exposed externally. It is less urgent than a server-side remote code execution issue, but still relevant for user trust and session protection.
Technical view
The Nim RST module permitted the javascript: URI scheme, creating CWE-79 XSS exposure in some applications using it, including NimForum. Nim 1.6.2 and later are fixed, with possible backports to earlier versions. NimForum 2.2.0 is fixed. CVSS is 6.1, network reachable, low complexity, no privileges, user interaction required.
Likely exposure
Exposure is likely limited to Nim applications that use the stdlib RST module to render user-controlled content. NimForum versions before 2.2.0 are specifically named. The source bundle does not enumerate other affected products or package identifiers.
Exploitation context
No source in the bundle reports active exploitation, and KEV is false. Exploitation depends on an application rendering attacker-controlled RST and a user interacting with resulting content. Impact is confidentiality and integrity through browser-side script execution, not direct server takeover.
Researcher notes
Focus assessment on trust boundaries around RST rendering. The CVE record gives fixed versions but incomplete affected-product enumeration. Avoid assuming every Nim application is vulnerable; validate actual use of the RST module and whether rendered output reaches browsers.
Mitigation direction
- Upgrade Nim to 1.6.2 or later where the RST fix is included.
- Upgrade NimForum to 2.2.0 or later if deployed.
- Check vendor guidance for supported backports on older Nim branches.
- Audit RST rendering paths that accept user-controlled content.
- Apply strict URI scheme allowlists in application-level rendering controls.
Validation and detection
- Inventory deployed Nim versions and identify any before 1.6.2.
- Identify applications using Nim stdlib RST with user-submitted content.
- Confirm NimForum deployments are version 2.2.0 or later.
- Review rendered links to ensure unsafe URI schemes are rejected.
- Document any older-version backport evidence from maintainers.
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-79: User-session and phishing behavior lookup
Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. 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-2021-46872 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
- 6.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/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:L/PR:N/UI:R/S:C/C:L/I:L/A:N2.82.7Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.1MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/nim-lang/nimforumCVE reference
- https://forum.nim-lang.org/t/8852CVE reference
- https://github.com/nim-lang/Nim/pull/19134CVE reference
- https://github.com/nim-lang/Nim/compare/v1.6.0...v1.6.2CVE reference
- https://github.com/nim-lang/Nim/commit/46275126b89218e64844eee169e8ced05dd0e2d7CVE reference
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 Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.