CVE-2026-123565

Description

Sveltejs devalue before 5.9.3 contains a resource exhaustion vulnerability where repeated primitive strings cause quadratic expansion in the uneval function. Attackers can supply a small crafted payload that is parsed and then passed to uneval, producing a very large serialized string that exhausts memory or CPU.

Overview

State: PUBLISHED
Assigner (CNA): VulnCheck
CVSS severity: HIGH
CVSS score: 8.7 / 10
CVSS vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Effective score: 8.7 / 10 HIGH source: CNA overview
CWE(s): CWE-400
Reserved: 2026-11-06
Published: 2026-11-08 01:38 UTC
Last updated: 2026-11-08 01:38 UTC
Source: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/123xxx/CVE-2026-123565.json
Linked Threat: CVE-2026-123565 — Devalue before 5.9.3 Quadratic Expansion Denial of Service via uneval

NVD triage scoring NVD CVE 2.0

Layer NVD adds on top of the CNA's CVE record — published / last-modified timestamps, exploitability / impact subscores, and the FIRST.org EPSS probability that this CVE will be exploited in the wild in the next 30 days.

NVD published: 2026-11-08 02:16:49 UTC
NVD last modified: 2026-11-08 02:16:49 UTC
NVD CVSS v3.1: 7.5 / 10 HIGH source: disclosure@vulncheck.com
NVD CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Exploitability subscore: 3.9 / 10
Impact subscore: 3.6 / 10
EPSS score: 0.0034 (probability of exploitation in next 30 days)
EPSS percentile: 28.07% vs all CVEs — higher = more likely to be exploited, as of 2026-11-08

European Union Vulnerability Database ENISA EUVD

ENISA's official EU repository for curated vulnerability intelligence. Carries a separate identifier (EUVD-YYYY-NNNN) and frequently exposes an earlier-published description + CVSS than NVD does.

EUVD ID: EUVD-2026-119450
Assigner: VulnCheck
Published: Nov 8, 2026, 1:38:04 AM
Updated: Nov 8, 2026, 1:38:04 AM
EUVD base score (CVSS 4.0): 8.7 / 10
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
EUVD-reported EPSS: 0.0000
Vendors: sveltejs
Products: devalue (0 <5.9.3)
Aliases: GHSA-m5fj-453c-wwq4

ENISA description: Sveltejs devalue before 5.9.3 contains a resource exhaustion vulnerability where repeated primitive strings cause quadratic expansion in the uneval function. Attackers can supply a small crafted payload that is parsed and then passed to uneval, producing a very large serialized string that exhausts memory or CPU.

EUVD references (2)

Affected products (1)

Vendor	Product	Versions	Platforms
sveltejs	devalue	`0` (affected), `5.9.3` (unaffected)	—

Vendor references (2)

References embedded in the original CVE record by the assigning CNA.

GitHub Security Advisory (GHSA-mcm9-63f2-9j32) vendor-advisory
VulnCheck Advisory: Devalue before 5.9.3 Quadratic Expansion Denial of Service via uneval third-party-advisory

MITRE references (2) cveawg.mitre.org

Pulled from MITRE's CVE Services API by the 🛰 Backfill from MITRE button.

GitHub Security Advisory (GHSA-mcm9-63f2-9j32) vendor-advisory
VulnCheck Advisory: Devalue before 5.9.3 Quadratic Expansion Denial of Service via uneval third-party-advisory

Web references (0)

DuckDuckGo results ranked by threat-intel / vendor advisory domains. Generated by the 🔎 Find references (web) button above — same flow as the Remediations search.

No web references attached yet.

NVD-tagged references (2)

Reference list NVD curates from the CNA record, vendor advisories, and third-party reports. The tag chips below are NVD's analyst-assigned categories.

https://github.com/sveltejs/devalue/security/advisories/GHSA-mcm9-63f2-9j32 disclosure@vulncheck.com
https://www.vulncheck.com/advisories/devalue-before-5.9.3-quadratic-expansion-denial-of-service-via-uneval disclosure@vulncheck.com

Remediations (10)

Remediations are stored against the linked Threat row; the list below is deduplicated across both pages.

CVE Database Search & Remediation Guidance

web:cvedatabase.com

Search and analyze CVE vulnerabilities with instant access to CVSS scores, affected products, and remediation guidance.

2026-11-08 10:24 UTC
CISA Requires Federal Agencies to Patch Critical Vulnerabilities Within ...

web:cybersecuritynews.com

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has issued Binding Operational Directive (BOD) 26-04, titled "Prioritizing Security Updates Based on Risk," compelling all Federal Civilian Executive Branch (FCEB) agencies to remediate the most dangerous known exploited vulnerabilities within just three calendar days.

2026-11-08 10:24 UTC
CVE Vulnerabilities 2026: Critical Flaws & Fixes Hub

web:cyberupdates365.com

Track critical CVE vulnerabilities 2026 with verified enterprise patch guides. Fix zero-days across VMware, WordPress, Windows, and cloud infrastructure.

2026-11-08 10:24 UTC
Cisco Meraki Security Hardening Release: October 2026

web:sec.cloudapps.cisco.com

As part of Cisco's ongoing commitment to proactive security and product quality, engineering teams conducted a comprehensive internal security review. This review resulted in software hardening releases that address multiple internally discovered vulnerabilities. These vulnerabilities were found during internal testing and are not known to be actively exploited. To assist customers in patching ...

2026-11-08 10:24 UTC
Microsoft Patch Tracker (November 2026): Exploit-Ranked | Senserva

web:senserva.com

Every Microsoft security patch (KB) and the CVEs it fixes, with severity, CVSS, and CISA KEV status. Cross-linked to the CVE reference.

2026-11-08 10:24 UTC
Portal for ArcGIS Security 2026 Update 3 Patch - Esri Support

web:support.esri.com

This patch deals specifically with the issues listed below under Issues Addressed with this Patch . As part of the patch installation, the Portal for ArcGIS service is stopped and restarted. The restart may take several minutes depending on the number of items on the enterprise deployment. As a best practice, clear the browser cache and re-launch the browser after installing the patch . This ...

2026-11-08 10:24 UTC
What Is CVE Remediation in 2026? - aikido.dev

web:www.aikido.dev

CVE remediation is fixing known flaws in the software you run. Why upgrading often fails, what remediation actually involves, and how backporting fixes it.

2026-11-08 10:24 UTC
Patch now: PHP2Shell, Brotli, and eMudhra guidance for customers

web:www.microsoft.com

The built-in PHP runtimes on App Service for Windows are end of life, so move those apps to App Service on Linux or bring your own supported PHP runtime. If you can't patch immediately: Apply the PHP project's interim mitigations and the Azure WAF protections. Note: This reduces exposure but doesn't fix the underlying vulnerabilities.

2026-11-08 10:24 UTC
The 8 Best Automated Vulnerability Remediation Tools in 2026

web:www.openhands.dev

Compare 8 automated vulnerability remediation tools for 2026 on fixes, prioritization, integrations, and deployment control.

2026-11-08 10:24 UTC
Oracle Critical Security Patch Update Advisory - September 2026

web:www.oracle.com

Prior Critical Patch Update and Critical Security Patch Update advisories should be reviewed for information regarding earlier published security patches. Refer to Critical Patch Updates, Critical Security Patch Updates, Security Alerts and Bulletins for information about Oracle Security advisories.

2026-11-08 10:24 UTC

AI Forensic Analysis

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Raw JSON

The full cvelistV5 record. Download as CVE-2026-123565.json.

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "packageURL": "pkg:npm/devalue",
          "product": "devalue",
          "vendor": "sveltejs",
          "versions": [
            {
              "lessThan": "5.9.3",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "5.9.3",
              "versionType": "semver"
            }
          ]
        }
      ],
      "cpeApplicability": [
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                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "credits": [
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          "type": "remediation developer",
          "value": "elliott-with-the-longest-name-on-github"
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      ],
      "datePublic": "2026-09-18T00:00:00.000Z",
      "descriptions": [
        {
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        }
      ],
      "metrics": [
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            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
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            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 8.7,
            "baseSeverity": "HIGH",
            "exploitMaturity": "NOT_DEFINED",
            "privilegesRequired": "NONE",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
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        },
        {
          "cvssV3_1": {
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            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
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            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "format": "CVSS"
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-400",
              "description": "Uncontrolled Resource Consumption",
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      "providerMetadata": {
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          "tags": [
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          ],
          "url": "https://github.com/sveltejs/devalue/security/advisories/GHSA-mcm9-63f2-9j32"
        },
        {
          "name": "VulnCheck Advisory: Devalue before 5.9.3 Quadratic Expansion Denial of Service via uneval",
          "tags": [
            "third-party-advisory"
          ],
          "url": "https://www.vulncheck.com/advisories/devalue-before-5.9.3-quadratic-expansion-denial-of-service-via-uneval"
        }
      ],
      "title": "Devalue before 5.9.3 Quadratic Expansion Denial of Service via uneval",
      "x_generator": {
        "engine": "vulncheck-endgame"
      }
    }
  },
  "cveMetadata": {
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    "datePublished": "2026-11-08T01:38:04.469Z",
    "dateReserved": "2026-11-06T00:53:14.312Z",
    "dateUpdated": "2026-11-08T01:38:04.469Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}