CVE-2026-21717
MEDIUMDescription
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**.
How to fix
This vulnerability affects an unusually large number of packages. The highest-confidence fixes are shown above; the full list is longer. Check the referenced advisories for complete coverage.
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Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Exploit Intelligence
Low risk: more likely to be exploited than 19% of all known CVEs.
References
Related Vulnerabilities
Other CWE-328 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2004-2761 | Critical | 9.8 | 9.9% | - | - |
| CVE-2024-54143 | Critical | 9.3 | 1.8% | - | - |
| CVE-2022-3433 | Medium | 6.5 | 0.8% | - | Fix |
| CVE-2022-29249 | High | 7.5 | 0.7% | - | - |
| CVE-2023-2900 | Low | 3.7 | 0.7% | - | - |
| CVE-2023-46233 | Critical | 9.1 | 0.6% | - | Fix |
Common questions
How do I fix CVE-2026-21717?
Published advisories record a fix for 75 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2026-21717 being actively exploited?
Not that we know of. CVE-2026-21717 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.27% is the estimated probability that it will be exploited in the next 30 days. That is higher than 19% of all scored CVEs.
How severe is CVE-2026-21717?
CVE-2026-21717 has a CVSS v3 base score of 5.9, rated moderate. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-21717 affect?
Published advisories record a fix for nodejs20 (Amazon), nodejs20-debuginfo (Amazon), nodejs20-debugsource (Amazon), nodejs20-devel (Amazon), and 71 more. Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-08-19.