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CVE-2026-15308 (GCVE-0-2026-15308)

Vulnerability from cvelistv5 – Published: 2026-07-09 17:10 – Updated: 2026-08-13 00:28
VLAI
Title
Incremental HTMLParser feed() allows CPU-exhaustion DoS via repeated unterminated markup declarations
Summary
The incremental HTML parser (html.parser.HTMLParser) allows for CPU denial-of-service through repeated unterminated markup declarations when processing uncontrolled data.
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-07-09 17:31 UTC
CWE
Assigner
Impacted products
Vendor Product Version CPE status
Python Software Foundation CPython Affected: 0 , < 3.10.21 (python)
Affected: 3.11.0 , < 3.11.16 (python)
Affected: 3.12.0 , < 3.12.14 (python)
Affected: 3.13.0 , < 3.13.15 (python)
Affected: 3.14.0 , < 3.14.7 (python)
Affected: 3.15.0a1 , < 3.15.0b4 (python)
guessed Create a notification for this product.
Show details on NVD website

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      "product_status:fixed": "767",
      "product_status:known_affected": "33",
      "product_status:known_not_affected": "35",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "python: Python: CPU Denial of Service in HTML parser via repeated unterminated markup declarations",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-15308.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-09-16T00:16:12Z",
      "cve": "CVE-2026-15308",
      "id": "CVE-2026-15308",
      "initial_release_date": "2026-07-11T03:28:42Z",
      "product_status:first_fixed": "52",
      "product_status:known_affected": "604",
      "product_status:recommended": "568",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-15308",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-15308.json",
      "version": "26"
    },
    "vulnrichment": {
      "containers": {
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          {
            "providerMetadata": {
              "dateUpdated": "2026-07-09T19:32:36.790Z",
              "orgId": "af854a3a-2127-422b-91ae-364da2661108",
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            },
            "references": [
              {
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              }
            ],
            "title": "CVE Program Container"
          },
          {
            "metrics": [
              {
                "other": {
                  "content": {
                    "id": "CVE-2026-15308",
                    "options": [
                      {
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                      },
                      {
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                      },
                      {
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                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2026-07-09T17:31:19.781935Z",
                    "version": "2.0.3"
                  },
                  "type": "ssvc"
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            ],
            "providerMetadata": {
              "dateUpdated": "2026-07-09T17:31:23.665Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
              "defaultStatus": "unaffected",
              "modules": [
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                "html"
              ],
              "product": "CPython",
              "repo": "https://github.com/python/cpython",
              "vendor": "Python Software Foundation",
              "versions": [
                {
                  "lessThan": "3.10.21",
                  "status": "affected",
                  "version": "0",
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                  "version": "3.11.0",
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                },
                {
                  "lessThan": "3.14.7",
                  "status": "affected",
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                },
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            }
          ],
          "credits": [
            {
              "lang": "en",
              "type": "reporter",
              "value": "Edward-x (https://github.com/YLChen-007)"
            },
            {
              "lang": "en",
              "type": "remediation developer",
              "value": "Serhiy Storchaka (https://github.com/serhiy-storchaka)"
            },
            {
              "lang": "en",
              "type": "remediation reviewer",
              "value": "Gregory P. Smith (https://github.com/gpshead)"
            },
            {
              "lang": "en",
              "type": "coordinator",
              "value": "Seth Larson (https://github.com/sethmlarson)"
            }
          ],
          "descriptions": [
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              "lang": "en",
              "supportingMedia": [
                {
                  "base64": false,
                  "type": "text/html",
                  "value": "The incremental HTML parser (html.parser.HTMLParser) allows for CPU\ndenial-of-service through repeated unterminated markup declarations when\nprocessing uncontrolled data."
                }
              ],
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          ],
          "metrics": [
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                "Automatable": "NOT_DEFINED",
                "Recovery": "NOT_DEFINED",
                "Safety": "NOT_DEFINED",
                "attackComplexity": "LOW",
                "attackRequirements": "NONE",
                "attackVector": "NETWORK",
                "baseScore": 8.7,
                "baseSeverity": "HIGH",
                "exploitMaturity": "NOT_DEFINED",
                "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"
              },
              "format": "CVSS",
              "scenarios": [
                {
                  "lang": "en",
                  "value": "GENERAL"
                }
              ]
            }
          ],
          "problemTypes": [
            {
              "descriptions": [
                {
                  "cweId": "CWE-400",
                  "description": "CWE-400",
                  "lang": "en",
                  "type": "CWE"
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          "providerMetadata": {
            "dateUpdated": "2026-08-13T00:28:26.690Z",
            "orgId": "28c92f92-d60d-412d-b760-e73465c3df22",
            "shortName": "PSF"
          },
          "references": [
            {
              "tags": [
                "vendor-advisory"
              ],
              "url": "https://mail.python.org/archives/list/security-announce@python.org/thread/F6453LWKSHKCTWFLCOURWPLETNUIW2Z5/"
            },
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          "source": {
            "discovery": "UNKNOWN"
          },
          "title": "Incremental HTMLParser feed() allows CPU-exhaustion DoS via repeated unterminated markup declarations",
          "x_generator": {
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          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "28c92f92-d60d-412d-b760-e73465c3df22",
        "assignerShortName": "PSF",
        "cveId": "CVE-2026-15308",
        "datePublished": "2026-07-09T17:10:57.317Z",
        "dateReserved": "2026-07-09T17:04:11.926Z",
        "dateUpdated": "2026-08-13T00:28:26.690Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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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

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.

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Detection rules are retrieved from Rulezet.

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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.


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