CVE-2026-21637 Denial of service in node
Remote attackers can crash Node.js TLS servers or exhaust resources by triggering unhandled exceptions in PSK or ALPN callbacks during the handshake.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-21637?
CVE-2026-21637 is a medium-severity denial of service vulnerability in Nodejs Node.js, published on 20 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
A flaw in Node.js TLS error handling allows remote attackers to crash or exhaust resources of a TLS server when `pskCallback` or `ALPNCallback` are in use. Synchronous exceptions thrown during these callbacks bypass standard TLS error handling paths (tlsClientError and error), causing either immediate process termination or silent file descriptor leaks that eventually lead to denial of service. Because these callbacks process attacker-controlled input during the TLS handshake, a remote client can repeatedly trigger the issue. This vulnerability affects TLS servers using PSK or ALPN callbacks across Node.js versions where these callbacks throw without being safely wrapped.
Weakness: CWE-400
Which versions are affected by CVE-2026-21637?
2 open source packages ship an affected version, including node and node-min. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
node Bitnami | All versions | 20.20.0, 22.22.0, 24.13.0, 25.3.0 |
node-min Bitnami | All versions | 20.20.0, 22.22.0, 24.13.0, 25.3.0 |
Products include Nodejs Node.js.
How do I fix CVE-2026-21637?
Upgrade node to a fixed version for your release line: 20.20.0, 22.22.0, 24.13.0 or 25.3.0.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-21637 being exploited?
There is no known exploitation of CVE-2026-21637 in the wild and no public exploit code.
Other vulnerabilities in Nodejs Node.js
Sources
Also known as ALPINE-CVE-2026-21637, AZL-75080, BELL-CVE-2026-21637, BIT-node-2026-21637, BIT-node-min-2026-21637, CLEANSTART-2026-ND53075 and 13 more.