CVE-2024-12254 (GCVE-0-2024-12254)

Vulnerability from cvelistv5 – Published: 2024-12-06 15:19 – Updated: 2026-07-31 14:08
VLAI
Title
Unbounded memory buffering in SelectorSocketTransport.writelines()
Summary
Starting in Python 3.12.0, the asyncio._SelectorSocketTransport.writelines() method would not "pause" writing and signal to the Protocol to drain the buffer to the wire once the write buffer reached the "high-water mark". Because of this, Protocols would not periodically drain the write buffer potentially leading to memory exhaustion. This vulnerability likely impacts a small number of users, you must be using Python 3.12.0 or later, on macOS or Linux, using the asyncio module with protocols, and using .writelines() method which had new zero-copy-on-write behavior in Python 3.12.0 and later. If not all of these factors are true then your usage of Python is unaffected.
Severity
8.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2024-12-06 15:35 UTC
CWE
  • CWE-400 - Uncontrolled Resource Consumption
  • CWE-770 - Allocation of Resources Without Limits or Throttling
Assigner
PSF CNA under the mitre root
CNA scorecard B 80/100 over 26 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Python Software Foundation CPython Affected: 0 , < 3.12.9 (python)
Affected: 3.13.0 , < 3.13.2 (python)
Affected: 3.14.0a1 , < 3.14.0a3 (python)
guessed Create a notification for this product.
python_software_foundation cpython Affected: 3.12.0 , < 3.14.0a1 (python)
    cpe:2.3:a:python_software_foundation:cpython:*:*:*:*:*:*:*:*
Create a notification for this product.
Credits
J. Nick Koston Seth Larson
Show details on NVD website
To clipboard 

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                      },
                      {
                        "Technical Impact": "partial"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2024-12-06T15:35:11.234951Z",
                    "version": "2.0.3"
                  },
                  "type": "ssvc"
                }
              }
            ],
            "problemTypes": [
              {
                "descriptions": [
                  {
                    "cweId": "CWE-770",
                    "description": "CWE-770 Allocation of Resources Without Limits or Throttling",
                    "lang": "en",
                    "type": "CWE"
                  }
                ]
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2024-12-06T15:37:21.821Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
              "defaultStatus": "unaffected",
              "modules": [
                "asyncio"
              ],
              "platforms": [
                "MacOS",
                "Linux"
              ],
              "product": "CPython",
              "repo": "https://github.com/python/cpython",
              "vendor": "Python Software Foundation",
              "versions": [
                {
                  "lessThan": "3.12.9",
                  "status": "affected",
                  "version": "0",
                  "versionType": "python"
                },
                {
                  "lessThan": "3.13.2",
                  "status": "affected",
                  "version": "3.13.0",
                  "versionType": "python"
                },
                {
                  "lessThan": "3.14.0a3",
                  "status": "affected",
                  "version": "3.14.0a1",
                  "versionType": "python"
                }
              ]
            }
          ],
          "credits": [
            {
              "lang": "en",
              "type": "reporter",
              "value": "J. Nick Koston"
            },
            {
              "lang": "en",
              "type": "coordinator",
              "value": "Seth Larson"
            }
          ],
          "descriptions": [
            {
              "lang": "en",
              "supportingMedia": [
                {
                  "base64": false,
                  "type": "text/html",
                  "value": "\u003cdiv\u003eStarting in Python 3.12.0, the asyncio._SelectorSocketTransport.writelines()\n method would not \"pause\" writing and signal to the Protocol to drain \nthe buffer to the wire once the write buffer reached the \"high-water \nmark\". Because of this, Protocols would not periodically drain the write\n buffer potentially leading to memory exhaustion.\u003cbr\u003e\u003c/div\u003e\u003cdiv\u003e\u003cbr\u003e\u003c/div\u003e\u003cdiv\u003eThis\n vulnerability likely impacts a small number of users, you must be using\n Python 3.12.0 or later, on macOS or Linux, using the asyncio module \nwith protocols, and using .writelines() method which had new \nzero-copy-on-write behavior in Python 3.12.0 and later. If not all of \nthese factors are true then your usage of Python is unaffected.\u003c/div\u003e\u003cbr\u003e"
                }
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            }
          ],
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            {
              "cvssV4_0": {
                "Automatable": "NOT_DEFINED",
                "Recovery": "NOT_DEFINED",
                "Safety": "NOT_DEFINED",
                "attackComplexity": "LOW",
                "attackRequirements": "NONE",
                "attackVector": "NETWORK",
                "baseScore": 8.7,
                "baseSeverity": "HIGH",
                "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:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
                "version": "4.0",
                "vulnAvailabilityImpact": "HIGH",
                "vulnConfidentialityImpact": "NONE",
                "vulnIntegrityImpact": "NONE",
                "vulnerabilityResponseEffort": "NOT_DEFINED"
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                  "value": "GENERAL"
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          ],
          "problemTypes": [
            {
              "descriptions": [
                {
                  "cweId": "CWE-400",
                  "description": "CWE-400 Uncontrolled Resource Consumption",
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            {
              "descriptions": [
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          "providerMetadata": {
            "dateUpdated": "2026-07-31T14:08:25.397Z",
            "orgId": "28c92f92-d60d-412d-b760-e73465c3df22",
            "shortName": "PSF"
          },
          "references": [
            {
              "tags": [
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              ],
              "url": "https://github.com/python/cpython/issues/127655"
            },
            {
              "tags": [
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              ],
              "url": "https://github.com/python/cpython/pull/127656"
            },
            {
              "tags": [
                "vendor-advisory"
              ],
              "url": "https://mail.python.org/archives/list/security-announce@python.org/thread/H4O3UBAOAQQXGT4RE3E4XQYR5XLROORB/"
            },
            {
              "tags": [
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            {
              "tags": [
                "patch"
              ],
              "url": "https://github.com/python/cpython/commit/e991ac8f2037d78140e417cc9a9486223eb3e786"
            }
          ],
          "source": {
            "discovery": "UNKNOWN"
          },
          "title": "Unbounded memory buffering in SelectorSocketTransport.writelines()",
          "x_generator": {
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          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "28c92f92-d60d-412d-b760-e73465c3df22",
        "assignerShortName": "PSF",
        "cveId": "CVE-2024-12254",
        "datePublished": "2024-12-06T15:19:41.576Z",
        "dateReserved": "2024-12-05T16:17:55.154Z",
        "dateUpdated": "2026-07-31T14:08:25.397Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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