CVE-2026-21717: nodejs node Use of Weak Hash

Vulnerability summary

CVE-2026-21717 is a medium (CVSS 5.9) Use of Weak Hash vulnerability in nodejs node. EPSS estimates a 0.27% chance of exploitation in the next 30 days, higher than 17.7% of scored vulnerabilities.

Timeline

1. 30-03-2026
   PublishedVulnerability first disclosed.
2. 10-05-2026
   Last modifiedVulnerability information updated.

Description

A flaw in V8's string hashing mechanism causes integer-like strings to be hashed to their numeric value, making hash collisions trivially predictable. By crafting a request that causes many such collisions in V8's internal string table, an attacker can significantly degrade performance of the Node.js process. The most common trigger is any endpoint that calls `JSON.parse()` on attacker-controlled input, as JSON parsing automatically internalizes short strings into the affected hash table. This vulnerability affects **20.x, 22.x, 24.x, and 25.x**.

• CWE-328Use of Weak HashThe product uses an algorithm that produces a digest (output value) that does not meet security expectations for a hash function that allows an adversary to reasonably determine the original input (preimage attack), find another input that can produce the same hash (2nd preimage attack), or find multiple inputs that evaluate to the same hash (birthday attack).