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Δ / VULNERABILITY RECORD

CVE-2026-21710.

Source-reported disclosure and enrichment record.

SEVERITY / CVSSHIGH / 7.5No severity score in this snapshot.
EXPLOITATION STATUSNot listed in the cached KEV catalogThis does not establish absence of exploitation.
RECORD STATUSMicrosoft vendor recordModified Oct 04, 2026

Disclosure summary

A flaw in Node.js HTTP request handling causes an uncaught `TypeError` when a request is received with a header named `__proto__` and the application accesses `req.headersDistinct`. When this occurs, `dest["__proto__"]` resolves to `Object.prototype` rather than `undefined`, causing `.push()` to be called on a non-array. This exception is thrown synchronously inside a property getter and cannot be intercepted by `error` event listeners, meaning it cannot be handled without wrapping every `req.headersDistinct` access in a `try/catch`. * This vulnerability affects all Node.js HTTP servers on **20.x, 22.x, 24.x, and v25.x**

Source-reported weakness categories

CWE-770

Source-specific records & product guidance

Sources retain their own attribution and scoring. Follow the original record to confirm affected versions, fixed releases, and configuration conditions.

Microsoft Security Updates (CVRF) · 2026-Mar

Open original source · Updated Oct 04, 2026

A flaw in Node.js HTTP request handling causes an uncaught `TypeError` when a request is received with a header named `__proto__` and the application accesses `req.headersDistinct`. When this occurs, `dest["__proto__"]` resolves to `Object.prototype` rather than `undefined`, causing `.push()` to be called on a non-array. This exception is thrown synchronously inside a property getter and cannot be intercepted by `error` event listeners, meaning it cannot be handled without wrapping every `req.headersDistinct` access in a `try/catch`. * This vulnerability affects all Node.js HTTP servers on **20.x, 22.x, 24.x, and v25.x**

Maximum of vendor-reported product scores; products and fixed builds are associations, not a universal affected-version statement.

Microsoft maximum product score: 7.5

VendorProduct / associationVersion / bounds
Microsoft update guidecbl2 nodejs18 18.20.3-12 (MSRC status code 3)
Microsoft update guidecbl2 nodejs18 18.20.3-12 on CBL Mariner 2.0 (MSRC status code 3)
Microsoft update guideazl3 nodejs 20.14.0-14 on Azure Linux 3.0 (MSRC status code 3)
Microsoft update guideazl3 nodejs24 24.13.0-3 on Azure Linux 3.0 (MSRC status code 3)
Microsoft update guideMicrosoft Visual Studio 2019 version 16.11 (includes 16.0 - 16.10) (MSRC status code 3)
Microsoft update guideMicrosoft Visual Studio 2022 version 17.14 (MSRC status code 3)
Microsoft update guidecbl2 nodejs18 18.20.3-12 on CBL-Mariner 2.0 (MSRC status code 3)

Vendor remediation references

  • CBL-Mariner Releases · build 20.14.0-15 · product IDs 21111-17084
  • Vendor guidance · product IDs 21111-17084
  • CBL-Mariner Releases · build 24.14.1-1 · product IDs 21059-17084
  • Vendor guidance · product IDs 21059-17084
  • Vendor guidance · build 16.11.59 · product IDs 11935
  • Vendor guidance · product IDs 11935
  • Vendor guidance · build 17.14.38 · product IDs 16767
  • Vendor guidance · product IDs 16767
  • Release Notes · product IDs 21130-21692
  • Vendor guidance · product IDs 21130-21692

Original records & references

PUBLISHED 2026-03-31T21:16:56-04:00
MODIFIED 2026-10-04T11:13:19-04:00
INGESTED 2026-10-08T12:45:08-04:00