Security readout for executives and security teams
Plain-English summary
CVE-2021-43309 is a denial-of-service risk in the uri-template-lite npm package. If an attacker can feed arbitrary input into URI.expand, processing can become exponentially expensive and reduce service availability. The sources do not show data theft or code execution.
Executive priority
Treat as a targeted availability risk, not a breach indicator. Prioritize internet-facing services or high-traffic APIs that use uri-template-lite with user input. Schedule remediation after critical exploitable code execution issues, unless the package sits on a business-critical public path.
Technical view
The issue is CWE-1333 ReDoS in uri-template-lite URI.expand. CVSS 3.1 is 5.9: network-reachable, high attack complexity, no privileges or user interaction, and high availability impact only. The source bundle identifies uri-template-lite version 0 as affected.
Likely exposure
Exposure is most likely in Node.js applications that depend on uri-template-lite and pass user-controlled strings to URI.expand. Services using only trusted templates or internal data have lower practical exposure. Confirm dependency versions because the bundle provides limited affected-version detail.
Exploitation context
CISA KEV is false, and the provided sources do not claim active exploitation. Exploitation requires attacker-controlled input reaching URI.expand and triggering excessive regex processing. Expected impact is service slowdown or outage, not confidentiality or integrity loss.
Researcher notes
Evidence is incomplete on exact fixed versions and exploitation history. The GitHub compare reference may show relevant changes between v22.1.0 and v22.9.0, but the bundle does not state a definitive patch. Validate from upstream before asserting remediation status.
Mitigation direction
- Inventory applications using the uri-template-lite npm package.
- Check vendor, JFrog, or npm guidance for fixed or safe versions.
- Avoid passing untrusted input directly to URI.expand.
- Constrain input length and format before expansion.
- Use application timeouts and resource limits around exposed request paths.
Validation and detection
- Search dependency manifests and lockfiles for uri-template-lite.
- Trace whether URI.expand receives external user-controlled input.
- Review public routes and APIs that process URI template values.
- Confirm deployed dependency versions against vendor guidance.
- Monitor affected endpoints for CPU spikes or request timeouts.
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-1333: 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-2021-43309 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:N/A:H
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:N/A:H2.23.6Primary 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:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://research.jfrog.com/vulnerabilities/uri-template-lite-redos-xray-211351/CVE reference · x_refsource_MISC
- https://github.com/litejs/uri-template-lite/compare/v22.1.0...v22.9.0CVE reference · x_refsource_MISC
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.
Inefficient Regular Expression Complexity
Inefficient Regular Expression Complexity represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.