CVE-2022-21208: 
JavaScript vulnerability analysis and mitigation

The vulnerability CVE-2022-21208 affects the node-opcua package versions before 2.74.0. This vulnerability was discovered and disclosed on August 22, 2022, and is related to a Denial of Service (DoS) condition in the package. The vulnerability stems from a missing limitation on the number of received chunks - both per single session and in total for all concurrent sessions (Snyk Advisory).

The vulnerability is classified as a Denial of Service (DoS) issue with a CVSS v3.1 Base Score of 7.5 (HIGH). The attack vector is network-based, with low attack complexity and requires no privileges or user interaction. The vulnerability exists due to the absence of proper chunk size validation in the packet assembly process. An attacker can exploit this by sending an unlimited number of huge chunks (e.g., 2GB each) without sending the Final closing chunk (NVD, Snyk Advisory).

A successful exploitation of this vulnerability can result in a total loss of availability of the affected system. The attack can cause the system to become unresponsive or crash, leading to a denial of service condition that persists until the attack stops. This impacts the availability of the service while leaving confidentiality and integrity unaffected (Snyk Advisory).

The vulnerability is considered highly exploitable due to its network-based attack vector and low complexity. Snyk has confirmed the existence of a proof-of-concept or detailed explanation of how to exploit this vulnerability. The EPSS score indicates a 0.17% (56th percentile) probability of exploitation in the wild (Snyk Advisory).

The recommended mitigation is to upgrade node-opcua to version 2.74.0 or higher. The fix includes implementation of proper chunk size verification and packet assembler refactoring, as evidenced by the commits in the node-opcua repository (GitHub Commit, GitHub Commit).