FKIE_CVE-2026-50029

Vulnerability from fkie_nvd - Published: 2026-08-14 19:17 - Updated: 2026-08-17 20:16
Severity
5.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Summary
js-toml is a TOML parser for JavaScript, Prior to version 1.1.2, the interpreter checks whether a key already exists in a parser-built container with `if (object[key])` instead of `if (key in object)`. When the prior value is a falsy primitive — `false`, `0`, `0n`, `0.0`, `-0`, or `""` — the duplicate-key branch is skipped and the value is silently overwritten by a later sub-table, dotted-key sub-table, or array-of-tables sharing the same name. Per the TOML 1.0.0 spec ("Defining a key multiple times is invalid"; "You cannot define any key or table more than once"), this should be a parse error. The result is structural type confusion of attacker-named keys in the value returned by `load()`. A boolean-typed `false` (or numeric `0`) becomes a truthy object. Host applications that gate behavior on `if (config.flag)`, `if (!user.banned)`, `if (config.allowDelete)`, or `if (config.publicMode)` will silently take the truthy branch. This is distinct from GHSA-65fc-cr5f-v7r2 (the 1.0.2 prototype-pollution fix). `Object.prototype` is not polluted. The `Object.create(null)` mitigation from 1.0.2 is intact; the bug here is in the duplicate-key state machine, not in container construction. Version 1.1.2 patches the incorrect comparison.
References
security-advisories@github.comhttps://github.com/sunnyadn/js-toml/commit/e0504fa5d3dcde2d1d588c9001c24b7b700beeeb
security-advisories@github.comhttps://github.com/sunnyadn/js-toml/releases/tag/v1.1.2
security-advisories@github.comhttps://github.com/sunnyadn/js-toml/security/advisories/GHSA-m34p-749j-x6m6
134c704f-9b21-4f2e-91b3-4a467353bcc0https://github.com/sunnyadn/js-toml/security/advisories/GHSA-m34p-749j-x6m6
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "js-toml",
          "vendor": "sunnyadn",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 1.1.2"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "js-toml is a TOML parser for JavaScript, Prior to version 1.1.2, the interpreter checks whether a key already exists in a parser-built container with `if (object[key])` instead of `if (key in object)`. When the prior value is a falsy primitive \u2014 `false`, `0`, `0n`, `0.0`, `-0`, or `\"\"` \u2014 the duplicate-key branch is skipped and the value is silently overwritten by a later sub-table, dotted-key sub-table, or array-of-tables sharing the same name. Per the TOML 1.0.0 spec (\"Defining a key multiple times is invalid\"; \"You cannot define any key or table more than once\"), this should be a parse error. The result is structural type confusion of attacker-named keys in the value returned by `load()`. A boolean-typed `false` (or numeric `0`) becomes a truthy object. Host applications that gate behavior on `if (config.flag)`, `if (!user.banned)`, `if (config.allowDelete)`, or `if (config.publicMode)` will silently take the truthy branch. This is distinct from GHSA-65fc-cr5f-v7r2 (the 1.0.2 prototype-pollution fix). `Object.prototype` is not polluted. The `Object.create(null)` mitigation from 1.0.2 is intact; the bug here is in the duplicate-key state machine, not in container construction. Version 1.1.2 patches the incorrect comparison."
    }
  ],
  "id": "CVE-2026-50029",
  "lastModified": "2026-08-17T20:16:43.660",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 5.3,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "LOW",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 1.4,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-50029",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-08-17T19:34:09.834226Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-08-14T19:17:18.980",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/sunnyadn/js-toml/commit/e0504fa5d3dcde2d1d588c9001c24b7b700beeeb"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/sunnyadn/js-toml/releases/tag/v1.1.2"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/sunnyadn/js-toml/security/advisories/GHSA-m34p-749j-x6m6"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/sunnyadn/js-toml/security/advisories/GHSA-m34p-749j-x6m6"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-697"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}



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