CVE-2026-33891 Forge has Denial of Service via Infinite Loop in BigInteger.modInverse() with Zero Input
An attacker can cause a denial of service by triggering an infinite loop in the BigInteger.modInverse function with zero input, hanging the application.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-33891?
CVE-2026-33891 is a high-severity denial of service vulnerability in digitalbazaar forge, published on 27 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Forge (also called `node-forge`) is a native implementation of Transport Layer Security in JavaScript. Prior to version 1.4.0, a Denial of Service (DoS) vulnerability exists in the node-forge library due to an infinite loop in the BigInteger.modInverse() function (inherited from the bundled jsbn library). When modInverse() is called with a zero value as input, the internal Extended Euclidean Algorithm enters an unreachable exit condition, causing the process to hang indefinitely and consume 100% CPU. Version 1.4.0 patches the issue.
Which versions are affected by CVE-2026-33891?
2 open source packages ship an affected version, including node-forge. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
node-forge npm | All versions | 1.4.0 |
node-forge npm | All versions | 1.4.0 |
Products include Digitalbazaar Forge.
How do I fix CVE-2026-33891?
Upgrade node-forge to 1.4.0 or later.
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-2026-33891 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-33891 exists.
Other vulnerabilities in digitalbazaar forge
Sources
Also known as CLEANSTART-2026-AG97190, CLEANSTART-2026-TT50115, CLEANSTART-2026-ZJ53876, CLSA-2026-1790542136, GHSA-5m6q-g25r-mvwx, MINI-2h52-wpw5-crhv and 20 more.