CVE-2026-21711 identifies a security flaw in the Node.js runtime environment version 25.x, specifically within its Permission Model's network enforcement mechanism. The vulnerability arises because Unix Domain Socket (UDS) server operations do not enforce the same permission checks as other network paths. Node.js introduced an experimental permission flag --allow-net to restrict network access, and when this flag is omitted, the expectation is that network operations are blocked. However, due to this flaw, code running with --permission but without --allow-net can still create and expose local IPC endpoints via UDS, circumventing the intended network restrictions. This means that processes can communicate locally through IPC channels that should have been blocked, potentially exposing sensitive data or enabling unauthorized local interactions. The vulnerability requires the attacker to have local code execution with limited privileges (PR:L) but does not require user interaction (UI:N). The CVSS v3.0 base score is 5.3, reflecting a medium severity impact with low attack complexity and limited scope. No known exploits have been reported in the wild, and no official patches or mitigations are linked yet. This issue primarily affects Node.js 25.x deployments that rely on the Permission Model with network restrictions enforced via the experimental --allow-net flag.

The primary impact of CVE-2026-21711 is the unintended exposure of local IPC endpoints via Unix Domain Sockets in Node.js 25.x environments configured to restrict network access. This can lead to unauthorized local communication between processes, potentially allowing an attacker with limited local privileges to bypass network restrictions and interact with other local services or processes. Confidentiality may be compromised if sensitive data is transmitted over these IPC channels. Integrity could be affected if unauthorized processes inject or manipulate data through these sockets. Availability impact is lower but possible if IPC misuse leads to resource exhaustion or service disruption. Organizations relying on Node.js for critical local IPC or enforcing strict network permission boundaries may face increased risk of local privilege escalation or lateral movement within the host. Since exploitation requires local access, remote attacks are not feasible, but insider threats or compromised local accounts could leverage this vulnerability. The lack of user interaction requirement facilitates automated exploitation once local access is obtained. Overall, this vulnerability weakens the security guarantees of Node.js's Permission Model and could undermine containment strategies in multi-tenant or restricted environments.

To mitigate CVE-2026-21711, organizations should first consider upgrading Node.js to a version where this vulnerability is patched once available. Until a patch is released, avoid relying solely on the experimental --allow-net flag for network restrictions in Node.js 25.x. Instead, implement additional OS-level controls such as mandatory access controls (e.g., SELinux, AppArmor) or containerization to isolate Node.js processes and restrict IPC access. Review and limit local user permissions to reduce the risk of unauthorized local code execution. Monitor Unix Domain Socket creation and usage on hosts running Node.js to detect anomalous IPC endpoints. Employ runtime security tools that can enforce IPC communication policies or alert on unexpected socket activity. For environments requiring strict network isolation, consider disabling or restricting Node.js features that enable IPC or network communication until the vulnerability is addressed. Finally, maintain strong local access controls and audit logs to detect potential exploitation attempts.