Security readout for executives and security teams
Plain-English summary
CVE-2026-21636 weakens Node.js’s experimental permission model in version 25. An application that believes network access is blocked may still connect to local Unix Domain Sockets. This could expose privileged local services or data if attacker-controlled input reaches networking options.
Executive priority
Prioritize review if Node.js v25 permission controls protect sensitive workloads or local services. This is not reported as actively exploited, but it can invalidate a security boundary and should be handled in normal vulnerability remediation cycles.
Technical view
When Node.js v25 runs with `--permission`, Unix Domain Socket connections can bypass intended network restrictions, even without `--allow-net`. Inputs such as URLs or `socketPath` options may reach local sockets through net, tls, or undici/fetch. The issue is categorized as CWE-284 and has CVSS 5.8 medium severity.
Likely exposure
Exposure is most likely in Node.js v25 deployments using the experimental permission model as a sandbox boundary, especially services accepting user-controlled URLs or socket configuration. Systems not using `--permission`, not on affected v25, or not relying on network restrictions appear less exposed based on the provided record.
Exploitation context
No active exploitation is stated in the provided sources, and CISA KEV is false. The practical risk depends on whether an attacker can influence networking inputs and whether sensitive local UDS services are reachable from the Node.js process.
Researcher notes
The record names only Node.js v25 and specifically lists 25.2.1. Network permissions are described as experimental. The provided bundle does not include exact fixed versions or detailed vendor workaround text, so remediation should be verified against the Node.js advisory.
Mitigation direction
- Review Node.js December 2025 security release guidance for fixed versions or official mitigations.
- Upgrade affected Node.js v25 deployments if the vendor advisory identifies a fixed release.
- Avoid treating experimental network permissions as a strong sandbox boundary.
- Restrict attacker control over URLs, socket paths, and fetch or client configuration.
- Limit access to sensitive local Unix Domain Sockets at the OS and service level.
Validation and detection
- Inventory Node.js versions and identify any v25.2.1 deployments.
- Check startup flags for `--permission` and absence of intended `--allow-net` access.
- Review code paths accepting user-controlled URLs or `socketPath` values.
- Identify local Unix Domain Sockets reachable by the Node.js process.
- Confirm remediation against the Node.js security advisory, not assumptions.
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
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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-284: Authorization and privilege behavior lookup
Authorization weaknesses can support privilege escalation and valid-account review, depending on exploit path. 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 lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupPrivilege behavior lookup
The CVE wording references privilege impact, so privilege escalation and authorization behavior review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-21636 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
- 5.8 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/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:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N3.91.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
5.8MediumVector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://nodejs.org/en/blog/vulnerability/december-2025-security-releasesCVE 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 Access Control
Improper Access Control represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.