GHSA-6V7P-G79W-8964

Vulnerability from github – Published: 2026-06-19 21:42 – Updated: 2026-06-19 21:42
VLAI
Summary
MessagePack for Python: Out-of-bounds read / crash on Unpacker reuse after a caught error
Details

Impact

If the Unpacker is used repeatedly after an error occurs, the process may crash with a SEGV.

If the Unpacker is used repeatedly to unpack untrusted input from external sources, it may be vulnerable to a DoS attack.

Patches

v1.2.1

Workarounds

Users should create a new Unpacker instead of reusing the same Unpacker after an error occurs.

Applying the above patch can prevent SEGV, but reusing the Streaming Unpacker after it has encountered an error will not yield correct data. If an error occurs during Streaming Unpacking, the Stream and Streaming Unpacker should be discarded.

Therefore, this is not just a workaround but the correct solution. The above patch only prevents crashes from incorrect usage.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Show details on source website
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.2.0"
      },
      "package": {
        "ecosystem": "PyPI",
        "name": "msgpack"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.2.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-416"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-19T21:42:55Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Impact\n\nIf the Unpacker is used repeatedly after an error occurs, the process may crash with a SEGV.\n\nIf the Unpacker is used repeatedly to unpack untrusted input from external sources, it may be vulnerable to a DoS attack.\n\n### Patches\n\nv1.2.1\n\n### Workarounds\n\nUsers should create a new Unpacker instead of reusing the same Unpacker after an error occurs.\n\nApplying the above patch can prevent SEGV, but reusing the Streaming Unpacker after it has encountered an error will not yield correct data. If an error occurs during Streaming Unpacking, the Stream and Streaming Unpacker should be discarded.\n\nTherefore, this is not just a workaround but the correct solution. The above patch only prevents crashes from incorrect usage.",
  "id": "GHSA-6v7p-g79w-8964",
  "modified": "2026-06-19T21:42:55Z",
  "published": "2026-06-19T21:42:55Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/msgpack/msgpack-python/security/advisories/GHSA-6v7p-g79w-8964"
    },
    {
      "type": "WEB",
      "url": "https://github.com/msgpack/msgpack-python/commit/2c56ddb5d0025ed481d962c0f5d62d19dec7476d"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/msgpack/msgpack-python"
    },
    {
      "type": "WEB",
      "url": "https://github.com/msgpack/msgpack-python/releases/tag/v1.2.1"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "MessagePack for Python: Out-of-bounds read / crash on Unpacker reuse after a caught error"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.

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

Author Source Type Date Other

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.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

JSON

Loading timeline…




    Related by attack behaviour

    Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.