FKIE_CVE-2026-54911

Vulnerability from fkie_nvd - Published: 2026-06-22 22:16 - Updated: 2026-06-26 20:10
Severity
6.5 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Summary
UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.13.0, ujson.dumps() (or ujson.dump() or ujson.encode()) have a reject_bytes=False option. When set, they may accept malformed or truncated UTF-8 byte sequences, silently rewriting them into different Unicode characters instead of rejecting them. This leads to input validation bypass and data integrity issues. This vulnerability is fixed in 5.13.0.
References
security-advisories@github.comhttps://github.com/ultrajson/ultrajson/commit/169eaf36b1116fece5034ee79a7a0ef3f6deedcfPatch
security-advisories@github.comhttps://github.com/ultrajson/ultrajson/releases/tag/5.13.0Product, Release Notes
security-advisories@github.comhttps://github.com/ultrajson/ultrajson/security/advisories/GHSA-3j69-69wj-xqx2Mitigation, Patch, Vendor Advisory
Impacted products
Vendor Product Version
ultrajson_project ultrajson *
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "ultrajson",
          "vendor": "ultrajson",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 5.13.0"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:ultrajson_project:ultrajson:*:*:*:*:*:python:*:*",
              "matchCriteriaId": "A5802005-78C3-4A11-B9DE-1CCD143A155B",
              "versionEndExcluding": "5.13.0",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.13.0, ujson.dumps() (or ujson.dump() or ujson.encode()) have a reject_bytes=False option. When set, they may accept malformed or truncated UTF-8 byte sequences, silently rewriting them into different Unicode characters instead of rejecting them. This leads to input validation bypass and data integrity issues. This vulnerability is fixed in 5.13.0."
    }
  ],
  "id": "CVE-2026-54911",
  "lastModified": "2026-06-26T20:10:54.850",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 6.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "LOW",
          "integrityImpact": "LOW",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 2.5,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-54911",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-06-23T14:19:57.855154Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-06-22T22:16:50.397",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch"
      ],
      "url": "https://github.com/ultrajson/ultrajson/commit/169eaf36b1116fece5034ee79a7a0ef3f6deedcf"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Product",
        "Release Notes"
      ],
      "url": "https://github.com/ultrajson/ultrajson/releases/tag/5.13.0"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Mitigation",
        "Patch",
        "Vendor Advisory"
      ],
      "url": "https://github.com/ultrajson/ultrajson/security/advisories/GHSA-3j69-69wj-xqx2"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-20"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}


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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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