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 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 h

CSIRTS triage

What: V8's string hashing algorithm hashes integer-like strings to their numeric value, allowing trivially predictable hash collisions.
Who is affected: JavaScript engines using V8 processing untrusted input that creates collisions in internal string tables.
Urgency: Medium priority; enables denial-of-service through hash collision attacks on V8 string internals.
Action: Update V8 engine to patched version; prioritize for systems processing untrusted JavaScript.

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EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-217170.27% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 18% of all EPSS-scored CVEs.

CVE	CSIRTS overview	External
CVE-2026-21717	coverage & exploitation status	NVD · CVE.org

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