CVE-2026-123561

Description

devalue before 5.9.3 allows malformed null-prototype object keys to bypass parse's __proto__ rejection through property-key coercion, an incomplete fix for GHSA-mwv9-gp5h-frr4. Attackers can supply crafted payloads that yield objects with a __proto__ own property, which alone does not cause prototype pollution.

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-2026-123561.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-2026-119446

EUVD enrichment is queued; refresh the page in a few seconds.

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-4q55-j62x-fr9h) vendor-advisory
VulnCheck Advisory: Sveltejs devalue before 5.9.3 __proto__ Rejection Bypass via Property-Key Coercion 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)

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
Security Advisories and Bulletins | Microsoft Learn

web:learn.microsoft.com

In this library you will find the following security documents that have been released by the Microsoft Security Response Center (MSRC). The MSRC investigates all reports of security vulnerabilities affecting Microsoft products and services, and releases these documents as part of the ongoing effort ...

2026-11-08 11:25 UTC
Security Update Guide - Microsoft

web:msrc.microsoft.com

The Microsoft Security Response Center (MSRC) investigates all reports of security vulnerabilities affecting Microsoft products and services, and provides the information here as part of the ongoing effort to help you manage security risks and help keep your systems protected.

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
ArcGIS Server Security 2026 Update 2 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 ArcGIS Server service is stopped and restarted. The restart may take several minutes depending on the number of services published on the ArcGIS Server site. This patch can be uninstalled as outlined in the Uninstalling this patch on Windows and Uninstalling ...

2026-11-08 11:25 UTC
ArcGIS Server Security 2026 Update 4 Patch - Esri Support

web:support.esri.com

The issues resolved by these patches are listed in the Issues addressed with this patch section below. As part of the patch installation, the ArcGIS Server service is stopped and restarted. The restart may take several minutes depending on the number of services published on the ArcGIS Server site. This patch can be uninstalled as outlined in the Uninstalling this patch on Windows and ...

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
Security Bulletin: IBM MQ is vulnerable to unauthenticated remote code ...

web:www.ibm.com

IBM MQ has addressed a JNDI injection vulnerability in the Jakarta Resource Adapter IVT servlet that could allow an unauthenticated remote attacker to execute ...

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

AI Forensic Analysis

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Raw JSON

The full cvelistV5 record. Download as CVE-2026-123561.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": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:a:svelte:devalue:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.9.3",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "credits": [
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          "lang": "en",
          "type": "remediation developer",
          "value": "elliott-with-the-longest-name-on-github"
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      ],
      "datePublic": "2026-09-18T00:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "devalue before 5.9.3 allows malformed null-prototype object keys to bypass parse's __proto__ rejection through property-key coercion, an incomplete fix for GHSA-mwv9-gp5h-frr4. Attackers can supply crafted payloads that yield objects with a __proto__ own property, which alone does not cause prototype pollution."
        }
      ],
      "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",
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            "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": "2026-11-08T01:38:01.726Z",
        "orgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
        "shortName": "VulnCheck"
      },
      "references": [
        {
          "name": "GitHub Security Advisory (GHSA-4q55-j62x-fr9h)",
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://github.com/sveltejs/devalue/security/advisories/GHSA-4q55-j62x-fr9h"
        },
        {
          "name": "VulnCheck Advisory: Sveltejs devalue before 5.9.3 __proto__ Rejection Bypass via Property-Key Coercion",
          "tags": [
            "third-party-advisory"
          ],
          "url": "https://www.vulncheck.com/advisories/sveltejs-devalue-before-5.9.3-proto-rejection-bypass-via-property-key-coercion"
        }
      ],
      "title": "Sveltejs devalue before 5.9.3 __proto__ Rejection Bypass via Property-Key Coercion",
      "x_generator": {
        "engine": "vulncheck-endgame"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
    "assignerShortName": "VulnCheck",
    "cveId": "CVE-2026-123561",
    "datePublished": "2026-11-08T01:38:01.726Z",
    "dateReserved": "2026-11-06T00:50:45.483Z",
    "dateUpdated": "2026-11-08T01:38:01.726Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}