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CVE Record

CVE-2026-21710: A flaw in Node.js HTTP request handling causes an uncaught `TypeError` when a request is received with a he...

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**

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A malformed HTTP request can crash affected Node.js servers when the application reads a specific request-header property. The impact is availability loss, not data theft. Public sources rate this high because it is network-reachable, needs no authentication, and can stop service if the vulnerable code path is hit.

Executive priority

Prioritize patching exposed Node.js services because this is a high-severity denial-of-service risk with simple network reachability. Treat it below remote code execution, but above routine dependency cleanup for customer-facing services.

Technical view

Node.js HTTP handling can throw an uncaught synchronous TypeError when a header named __proto__ is present and application code accesses req.headersDistinct. The issue comes from prototype resolution causing push() to run on a non-array. The exception is not caught by ordinary error event listeners. CVSS is 7.5, availability-only.

Likely exposure

Most relevant exposure is internet-facing Node.js HTTP services on affected Node.js lines that read req.headersDistinct directly or through middleware. The provided record names Node.js 20.x, 22.x, 24.x, and v25.x HTTP servers, with additional version data requiring vendor confirmation.

Exploitation context

The bundle does not show CISA KEV listing or active exploitation evidence. The attack conditions are low complexity and unauthenticated over the network, but only applications reaching req.headersDistinct appear directly triggerable.

Researcher notes

Evidence supports a targeted availability bug in Node.js HTTP header handling. Version details in the supplied bundle are partially ambiguous, so use upstream Node.js and distributor advisories as authority for exact fixed and affected builds.

Mitigation direction

  • Apply the official Node.js March 2026 security releases where applicable.
  • For Red Hat builds, follow the linked RHSA advisories for package updates.
  • Inventory services using Node.js HTTP servers on the affected release lines.
  • Review code and dependencies for req.headersDistinct access.
  • Use temporary defensive try/catch only where vendor updating is blocked.

Validation and detection

  • Confirm deployed Node.js versions across production, CI, containers, and base images.
  • Check whether application or middleware reads req.headersDistinct.
  • Verify updated packages match Node.js or Red Hat advisory guidance.
  • Run regression tests for HTTP request handling after updating.
  • Monitor service crash logs for uncaught TypeError in header handling.
Prepared
Confidence
medium
Sources
12

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-770: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cwe · low confidence lookup

CWE-843: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-21710 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.0)
Known Exploited
No
Published

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
17Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.5CVSS 3.0HighCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6hackerone
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-21710Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPNode.js: Node.js: Denial of Service due to crafted HTTP `__proto__` header
other:Red Hat severity ratingcvssV3_1
  • 2026-03-30T20:01:21.196Z: Reported to Red Hat.
  • 2026-03-30T19:07:28.558Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
nodejsnode20.20.1, 22.22.1, 24.14.0, 25.8.1, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0unaffected
Weakness

CWE details

CWE-770CWE-843

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.