CVE-2026-21717
V8's string hashing mechanism causes integer-like strings to be hashed to their numeric value vulnerability
V8s · 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**.
MSRC advisory May 31, 2026
Alert details
- Source feed
- Microsoft MSRC
- CVE ID
- CVE-2026-21717
- CWE
- CWE-328
- Affected products
- 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**. · A 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**. · A
What happened
Information published.
What it means for your business
A 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**. (CVE-2026-21717) was added to Microsoft’s security update guidance. Information published. PremierePC tracks MSRC advisories for Upstate SC businesses — patch or open a ticket if you need help verifying exposure.
CVSS score
5.9 (Medium)
EPSS probability
0.28%
Sources
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