Security readout for executives and security teams
Plain-English summary
semver-regex, an npm package for matching semantic versions, can consume excessive CPU when testing attacker-controlled input. The business impact is availability: services using it on exposed request paths could slow down or become unavailable under crafted input.
Executive priority
Treat as a moderate availability risk. Prioritize internet-facing services and high-traffic APIs first, especially where dependency ownership is unclear or input validation is weak.
Technical view
CVE-2021-43307 is an exponential Regular Expression Denial of Service in semver-regex when arbitrary input reaches the package's test() method. The CVSS 3.1 score is 5.9, with network attack vector, high complexity, no privileges, no user interaction, and availability impact only.
Likely exposure
Exposure is most likely in Node.js applications that depend on semver-regex and apply it directly or indirectly to untrusted strings, such as API parameters, uploaded content, package metadata, or form fields.
Exploitation context
The supplied sources describe a trigger condition but do not cite public exploitation. The CVE is not listed as KEV in the provided bundle, so active exploitation should not be assumed from this evidence.
Researcher notes
The affected version range is unspecified in the provided bundle. Analysis should focus on reachability: dependency presence alone is less important than whether attacker-controlled input reaches semver-regex test(). Avoid claiming a fixed version without vendor evidence.
Mitigation direction
- Inventory applications and lockfiles for semver-regex usage.
- Check semver-regex, npm, and JFrog guidance for fixed versions or replacement advice.
- Reduce exposure of code paths that test arbitrary user input.
- Apply conservative input length limits before regex evaluation where feasible.
- Monitor affected services for CPU saturation and request latency spikes.
Validation and detection
- Search dependency manifests and lockfiles for semver-regex.
- Trace whether semver-regex test() receives attacker-controlled input.
- Confirm whether affected code is reachable from public or authenticated routes.
- Review dependency advisory tooling results against CVE-2021-43307.
- Document any compensating controls if no vendor fix is confirmed.
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
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CWE-1333: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-43307 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/semver-regex-redos-xray-211349/CVE 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.