undici is an HTTP client library for Node.js. In versions 5.15.0 through 6.29.0, 7.0.0 through 7.30.0, and 8.0.0 through 8.12.1, its WebSocket client, including the bundled WebSocket exposed by Node.js, can be driven to exhaust process memory by a malicious or compromised WebSocket server. For every PING frame received, the client automatically writes a PONG response and ignores the backpressure signal from the socket write, so a server that streams small PING frames while never reading the clients PONGs makes the outbound write queue and heap grow without bound until the Node.js process runs out of memory and terminates. The attack is remote and unauthenticated, needs only a normal WebSocket connection, and is asymmetric, since small inbound PINGs produce a much larger retained outbound queue, with availability the only impact. The issue is fixed in undici 6.29.1, 7.30.1, and 8.12.2, which pause WebSocket frame parsing when the automatic PONG response hits socket backpressure and resume on drain, bounding the outbound queue, and users should upgrade to one of those versions or later. There is no workaround.
Weakness
The product does not properly control the allocation and maintenance of a limited resource.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Undici | Nodejs | 5.15.0 (including) | 6.29.1 (excluding) |
| Undici | Nodejs | 7.0.0 (including) | 7.30.1 (excluding) |
| Undici | Nodejs | 8.0.0 (including) | 8.12.2 (excluding) |
| Red Hat Hardened Images | RedHat | nodejs26-main-11.20.0-1.26.11.1.0.4.hum1 | * |
| Red Hat Hardened Images | RedHat | nodejs24-main-11.19.0-1.24.21.0.1.5.hum1 | * |
| Red Hat Hardened Images | RedHat | nodejs24-main-24.21.0-1.5.hum1 | * |
| Red Hat Hardened Images | RedHat | nodejs26-main-11.20.0-1.26.12.1.0.1.hum1 | * |
| Red Hat Hardened Images | RedHat | nodejs26-main-26.12.1-0.1.hum1 | * |
| Node-undici | Ubuntu | upstream | * |
Potential Mitigations
Mitigation of resource exhaustion attacks requires that the target system either:
The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.
The second solution is simply difficult to effectively institute – and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/147.html
- https://cwe.mitre.org/data/definitions/227.html
- https://cwe.mitre.org/data/definitions/492.html