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PYSEC-2026-1056

Vulnerability from pysec - Published: 2026-07-06 08:03 - Updated: 2026-07-07 11:31
VLAI
Details

Impact

What kind of vulnerability is it? Who is impacted?

When an error occurs while reallocating the buffer for string decoding, the buffer gets freed twice.

Due to how UltraJSON uses the internal decoder, this double free is impossible to trigger from Python.

Patches

Has the problem been patched? What versions should users upgrade to?

Users should upgrade to UltraJSON 5.4.0.

Workarounds

Is there a way for users to fix or remediate the vulnerability without upgrading?

There is no workaround.

For more information

If you have any questions or comments about this advisory: * Open an issue in UltraJSON

Severity
5.9 (Medium)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Impacted products
Name purl
ujson pkg:pypi/ujson
Aliases
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "ujson",
        "purl": "pkg:pypi/ujson"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "5.4.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.15",
        "1.18",
        "1.19",
        "1.21",
        "1.22",
        "1.23",
        "1.30",
        "1.33",
        "1.34",
        "1.35",
        "1.4",
        "1.6",
        "1.8",
        "1.9",
        "2.0.0",
        "2.0.1",
        "2.0.2",
        "2.0.3",
        "3.0.0",
        "3.1.0",
        "3.2.0",
        "4.0.0",
        "4.0.1",
        "4.0.2",
        "4.1.0",
        "4.2.0",
        "4.3.0",
        "5.0.0",
        "5.1.0",
        "5.2.0",
        "5.3.0"
      ]
    }
  ],
  "aliases": [
    "CVE-2022-31117",
    "GHSA-fm67-cv37-96ff"
  ],
  "details": "### Impact\n_What kind of vulnerability is it? Who is impacted?_\n\nWhen an error occurs while reallocating the buffer for string decoding, the buffer gets freed twice.\n\nDue to how UltraJSON uses the internal decoder, this double free is impossible to trigger from Python.\n\n### Patches\n_Has the problem been patched? What versions should users upgrade to?_\n\nUsers should upgrade to UltraJSON 5.4.0.\n\n### Workarounds\n_Is there a way for users to fix or remediate the vulnerability without upgrading?_\n\nThere is no workaround.\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Open an issue in [UltraJSON](http://github.com/ultrajson/ultrajson/issues)\n",
  "id": "PYSEC-2026-1056",
  "modified": "2026-07-07T11:31:24.124624Z",
  "published": "2026-07-06T08:03:30.989917Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/ultrajson/ultrajson/security/advisories/GHSA-fm67-cv37-96ff"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2022-31117"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ultrajson/ultrajson/commit/9c20de0f77b391093967e25d01fb48671104b15b"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/ultrajson/ultrajson"
    },
    {
      "type": "WEB",
      "url": "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/NAU5N4A7EUK2AMUCOLYDD5ARXAJYZBD2"
    },
    {
      "type": "WEB",
      "url": "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/OPPU5FZP3LCTXYORFH7NHUMYA5X66IA7"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/ujson"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-fm67-cv37-96ff"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Potential double free of buffer during string decoding"
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


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