CVE-2026-123567

Description

Sveltejs devalue before 5.6.4 contains a prototype injection vulnerability that allows attackers to inject __proto__ own properties into objects returned by devalue.parse and devalue.unflatten. Attackers can supply crafted serialized input that, when downstream code merges results via Object.assign, alters the target object's prototype.

Overview

State: PUBLISHED
Assigner (CNA): VulnCheck
CVSS severity: MEDIUM
CVSS score: 6.3 / 10
CVSS vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Effective score: 6.3 / 10 MEDIUM source: CNA overview
CWE(s): CWE-1321
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-2026-123567.json

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-2026-119452

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Affected products (1)

Vendor	Product	Versions	Platforms
sveltejs	devalue	`0` (affected), `5.6.4` (unaffected)	—

Vendor references (2)

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

GitHub Security Advisory (GHSA-mwv9-gp5h-frr4) vendor-advisory
VulnCheck Advisory: Sveltejs devalue before 5.6.4 Prototype Injection via parse and unflatten 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.

Remediations (10)

CVEs and Security Vulnerabilities - OpenCVE

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2026-11-08 11:25 UTC
October 2026 Critical Patch Update Released | security

web:blogs.oracle.com

For more information about the Critical Patch Update program, see the security vulnerability remediation practices page located on the Oracle Trust Center.

2026-11-08 11:25 UTC
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 11:25 UTC
Remediate vulnerabilities | Security Advisory | NetScaler

web:docs.netscaler.com

NetScaler detects CVEs and provides remediation suggestions the same. This topic lists the remediations suggested for the following CVEs :

2026-11-08 11:25 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 11:25 UTC
Microsoft Patch Tracker (October 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 11:25 UTC
SAP Security Patch Day - October 2026

web:support.sap.com

On 13 th of October 2026 , SAP security patch day saw the release of 16 new security notes and 4 GitHub security advisories. There are 2 updates to previously released security notes.

2026-11-08 11:25 UTC
Oracle Critical Patch Update Advisory - July 2026

web:www.oracle.com

This Critical Patch Update contains 1448 new security patches across the product families listed below. Please note that a My Oracle Support (MOS) note summarizing the content of this Critical Patch Update and other Oracle Software Security Assurance activities is located at July 2026 Critical Patch Update: Executive Summary and Analysis.

2026-11-08 11:25 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 11:25 UTC
CVE-2026-123567: Vulnerability Details - Analysis & Fix | TheHackerWire

web:www.thehackerwire.com

How do I fix or mitigate CVE-2026-123567 ? To protect against CVE-2026-123567 , you should: (1) Apply the latest security patches from the vendor, (2) Check official security advisories for specific remediation steps, (3) Update affected software to the latest version, and (4) Monitor your systems for any signs of exploitation.

2026-11-08 11:25 UTC

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Raw JSON

The full cvelistV5 record. Download as CVE-2026-123567.json.

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "packageURL": "pkg:npm/devalue",
          "product": "devalue",
          "vendor": "sveltejs",
          "versions": [
            {
              "lessThan": "5.6.4",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "5.6.4",
              "versionType": "semver"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:a:svelte:devalue:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.6.4",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "remediation developer",
          "value": "elliott-with-the-longest-name-on-github"
        },
        {
          "lang": "en",
          "type": "remediation reviewer",
          "value": "KarimPwnz"
        },
        {
          "lang": "en",
          "type": "remediation reviewer",
          "value": "wim-vercel"
        },
        {
          "lang": "en",
          "type": "reporter",
          "value": "mattiasljungstrom"
        }
      ],
      "datePublic": "2026-03-11T00:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "Sveltejs devalue before 5.6.4 contains a prototype injection vulnerability that allows attackers to inject __proto__ own properties into objects returned by devalue.parse and devalue.unflatten. Attackers can supply crafted serialized input that, when downstream code merges results via Object.assign, alters the target object's prototype."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "baseScore": 6.3,
            "baseSeverity": "MEDIUM",
            "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:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "LOW",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "format": "CVSS"
        },
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 3.7,
            "baseSeverity": "LOW",
            "confidentialityImpact": "NONE",
            "integrityImpact": "LOW",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N",
            "version": "3.1"
          },
          "format": "CVSS"
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-1321",
              "description": "Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-11-08T01:38:05.840Z",
        "orgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
        "shortName": "VulnCheck"
      },
      "references": [
        {
          "name": "GitHub Security Advisory (GHSA-mwv9-gp5h-frr4)",
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://github.com/sveltejs/devalue/security/advisories/GHSA-mwv9-gp5h-frr4"
        },
        {
          "name": "VulnCheck Advisory: Sveltejs devalue before 5.6.4 Prototype Injection via parse and unflatten",
          "tags": [
            "third-party-advisory"
          ],
          "url": "https://www.vulncheck.com/advisories/sveltejs-devalue-before-5.6.4-prototype-injection-via-parse-and-unflatten"
        }
      ],
      "title": "Sveltejs devalue before 5.6.4 Prototype Injection via parse and unflatten",
      "x_generator": {
        "engine": "vulncheck-endgame"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
    "assignerShortName": "VulnCheck",
    "cveId": "CVE-2026-123567",
    "datePublished": "2026-11-08T01:38:05.840Z",
    "dateReserved": "2026-11-06T00:53:14.312Z",
    "dateUpdated": "2026-11-08T01:38:05.840Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}