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Node.Js CVE-2026-21637

HIGH
Uncontrolled Resource Consumption (CWE-400)
2026-01-20 support@hackerone.com
Denial Of Service TLS Node.js Red Hat Node.Js Suse
7.5
CVSS 3.1 · NVD
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Initiate TLS handshake with crafted PSK or ALPN
  2. Delivery
    Trigger synchronous exception in callback
  3. Exploit
    Bypass error handling paths
  4. Execution
    Crash process or leak file descriptors
  5. Impact
    Exhaust server resources

Vulnerability Assessment

Weakness
CWE
CWE-400
OWASP Top 10:2025
A06:2025 - Insecure Design
ASVS 5.0
V2 - Validation and Business Logic Resource consumption limits
MITRE ATT&CK

1 technique across 1 tactic: Impact

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

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Exploitation Conditions

Node.js TLS server with pskCallback or ALPNCallback enabled. Attacker must be able to initiate TLS handshakes to the server; no authentication required.
Impact

CVSS 7.5 (HIGH). Attack vector: Network. Complexity: Low. Privileges required: None. User interaction: None. Exploitable via remote/network.
Exploit ScenarioDerived

A remote attacker could exploit this vulnerability to crash or exhaust resources of a TLS server when pskCallback or ALPNCallback.
This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 12, 2026

Node.js TLS servers using PSK or ALPN callbacks are vulnerable to denial of service when these callbacks throw unhandled synchronous exceptions during the TLS handshake. Remote attackers can exploit this by sending specially crafted TLS handshake requests to trigger resource exhaustion or process crashes, either through immediate termination or silent file descriptor leaks. No patch is currently available for this vulnerability.

Earlier versions of this analysis (1)
v1 Mar 12, 2026 - 21:54 CVSS 7.5

A flaw in Node.js TLS error handling allows remote attackers to crash or exhaust resources of a TLS server when pskCallback or ALPNCallback are in use. [CVSS 7.5 HIGH]

RemediationAI

Monitor vendor advisories for a patch. Restrict network access to the affected service where possible.

Affects your stack

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Technical ContextAI · show details

Classified as CWE-400 (Uncontrolled Resource Consumption). Affects Node.Js. A flaw in Node.js TLS error handling allows remote attackers to crash or exhaust resources of a TLS server when pskCallback or ALPNCallback are in use. Synchronous exceptions thrown during these callbacks bypass standard TLS error handling paths (tlsClientError and error), causing either immediate process termination or silent file descriptor leaks that eventually lead to denial of service. Because these callbacks process attacker-controlled input during the TLS handshake, a remote client ca

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Severity by source

NVD PRIMARY 7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SUSE 5.9 MEDIUM
AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Red Hat 5.9 MEDIUM

Primary rating from NVD.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Lifecycle Timeline

2
Patch released
Apr 09, 2026 - 14:30 nvd
Patch available
CVE Published
Jan 20, 2026 - 21:16 nvd
HIGH 7.5

DescriptionCVE.org

A flaw in Node.js TLS error handling allows remote attackers to crash or exhaust resources of a TLS server when pskCallback or ALPNCallback are in use. Synchronous exceptions thrown during these callbacks bypass standard TLS error handling paths (tlsClientError and error), causing either immediate process termination or silent file descriptor leaks that eventually lead to denial of service. Because these callbacks process attacker-controlled input during the TLS handshake, a remote client can repeatedly trigger the issue. This vulnerability affects TLS servers using PSK or ALPN callbacks across Node.js versions where these callbacks throw without being safely wrapped.

Executive ViewAI

Why It Matters

Organizations using A flaw in Node.js TLS error handling face notable risk from CVE-2026-21637, a resource exhaustion vulnerability rated CVSS 7.5. Exploitation could cause service disruption or denial of service, impacting availability for legitimate users. Organizations should apply vendor updates when available and consider compensating controls in the interim.

Business Impact: High
Compensating Controls

Apply vendor patch. If immediate patching is not feasible: (1) Implement network-level access controls to limit exposure; (2) Enable enhanced monitoring and alerting; (3) Apply principle of least privilege.

Threat Intelligence Overview

EPSS Score
0.0%
Top 90% exploitable
Data Quality
3 sources
Confidence: Low
NVD CVE.org EPSS Vendor

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC No
EPSS 0.0%
Patch available Yes
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
Yes
Human Impact
High

Priority Score

38
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +38
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Denial of Service MEDIUM

Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.

Affected Products (CPE)CVE.org

cpe:2.3:a:nodejs:node.js:*:*:*:*:-:*:*:*
cpe:2.3:a:nodejs:node.js:*:*:*:*:-:*:*:*
cpe:2.3:a:nodejs:node.js:*:*:*:*:-:*:*:*
cpe:2.3:a:nodejs:node.js:*:*:*:*:-:*:*:*

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Vendor StatusVendor

SUSE

Severity: Medium
Product Status
Container suse/sl-micro/6.0/kvm-os-container:2.1.3-6.15 Affected
SUSE Liberty Linux 8 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS Fixed
SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS Fixed
SUSE Linux Enterprise High Performance Computing 15 SP7 SUSE Linux Enterprise Module for Web and Scripting 15 SP7 SUSE Linux Enterprise Server 15 SP7 SUSE Linux Enterprise Server for SAP Applications 15 SP7 Fixed

References

Advisories & patches
ADVISORY https://access.redhat.com/errata/RHSA-2026:1842 ADVISORY https://access.redhat.com/errata/RHSA-2026:1843 ADVISORY https://access.redhat.com/errata/RHSA-2026:2420 ADVISORY https://access.redhat.com/errata/RHSA-2026:2421 ADVISORY https://access.redhat.com/errata/RHSA-2026:2422 ADVISORY https://access.redhat.com/errata/RHSA-2026:2767 ADVISORY https://access.redhat.com/errata/RHSA-2026:2768 ADVISORY https://access.redhat.com/errata/RHSA-2026:2781 ADVISORY https://access.redhat.com/errata/RHSA-2026:2782 ADVISORY https://access.redhat.com/errata/RHSA-2026:2783 ADVISORY https://access.redhat.com/errata/RHSA-2026:2864 ADVISORY https://access.redhat.com/errata/RHSA-2026:2899 ADVISORY https://nodejs.org/en/blog/vulnerability/december-2025-security-releases ADVISORY https://www.herodevs.com/vulnerability-directory/cve-2026-21637 ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:0295/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:0301/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:0435/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:0457/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:20436/

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