CVE-2026-81724 (GCVE-0-2026-81724)
Vulnerability from cvelistv5
Published
2026-08-27 14:51
Modified
2026-08-27 18:29
CWE
Summary
NLTK before 3.10.3 contains an uncontrolled recursion vulnerability in nltk.featstruct.FeatStructReader that allows unauthenticated attackers to cause a denial of service by supplying deeply nested feature-structure input. Attackers can craft trivial payloads with nested brackets that exceed Python's recursion limit and raise an unhandled RecursionError, crashing applications that parse user-supplied feature structures or feature grammars.
Impacted products
Vendor Product Version
nltk nltk Version: 0   
Create a notification for this product.
Show details on NVD website


{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-81724",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-27T18:28:30.462220Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-08-27T18:29:04.021Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/nltk/nltk/security/advisories/GHSA-cw6x-m8jw-qmrh"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "packageURL": "pkg:pypi/nltk",
          "product": "nltk",
          "vendor": "nltk",
          "versions": [
            {
              "lessThan": "3.10.3",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "3.10.3",
              "versionType": "semver"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "3.10.3",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "reporter",
          "value": "JoshgunAbdullayev"
        }
      ],
      "datePublic": "2026-08-12T00:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "NLTK before 3.10.3 contains an uncontrolled recursion vulnerability in nltk.featstruct.FeatStructReader that allows unauthenticated attackers to cause a denial of service by supplying deeply nested feature-structure input. Attackers can craft trivial payloads with nested brackets that exceed Python\u0027s recursion limit and raise an unhandled RecursionError, crashing applications that parse user-supplied feature structures or feature grammars."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 6.9,
            "baseSeverity": "MEDIUM",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "LOW",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE"
          },
          "format": "CVSS"
        },
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "LOW",
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
            "version": "3.1"
          },
          "format": "CVSS"
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-674",
              "description": "Uncontrolled Recursion",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-27T14:51:17.358Z",
        "orgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
        "shortName": "VulnCheck"
      },
      "references": [
        {
          "name": "GitHub Security Advisory (GHSA-cw6x-m8jw-qmrh)",
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://github.com/nltk/nltk/security/advisories/GHSA-cw6x-m8jw-qmrh"
        },
        {
          "name": "VulnCheck Advisory: NLTK before 3.10.3 Denial of Service via Uncontrolled Recursion",
          "tags": [
            "third-party-advisory"
          ],
          "url": "https://www.vulncheck.com/advisories/nltk-before-3.10.3-denial-of-service-via-uncontrolled-recursion"
        }
      ],
      "title": "NLTK before 3.10.3 Denial of Service via Uncontrolled Recursion",
      "x_generator": {
        "engine": "vulncheck-endgame"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
    "assignerShortName": "VulnCheck",
    "cveId": "CVE-2026-81724",
    "datePublished": "2026-08-27T14:51:17.358Z",
    "dateReserved": "2026-08-27T11:15:29.420Z",
    "dateUpdated": "2026-08-27T18:29:04.021Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "vulnrichment": {
      "containers": "{\"cna\": {\"providerMetadata\": {\"orgId\": \"83251b91-4cc7-4094-a5c7-464a1b83ea10\", \"shortName\": \"VulnCheck\", \"dateUpdated\": \"2026-08-27T14:51:17.358Z\"}, \"datePublic\": \"2026-08-12T00:00:00.000Z\", \"title\": \"NLTK before 3.10.3 Denial of Service via Uncontrolled Recursion\", \"descriptions\": [{\"lang\": \"en\", \"value\": \"NLTK before 3.10.3 contains an uncontrolled recursion vulnerability in nltk.featstruct.FeatStructReader that allows unauthenticated attackers to cause a denial of service by supplying deeply nested feature-structure input. Attackers can craft trivial payloads with nested brackets that exceed Python\u0027s recursion limit and raise an unhandled RecursionError, crashing applications that parse user-supplied feature structures or feature grammars.\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"description\": \"Uncontrolled Recursion\", \"cweId\": \"CWE-674\", \"type\": \"CWE\"}]}], \"affected\": [{\"vendor\": \"nltk\", \"product\": \"nltk\", \"defaultStatus\": \"unaffected\", \"packageURL\": \"pkg:pypi/nltk\", \"versions\": [{\"version\": \"0\", \"status\": \"affected\", \"versionType\": \"semver\", \"lessThan\": \"3.10.3\"}, {\"version\": \"3.10.3\", \"status\": \"unaffected\", \"versionType\": \"semver\"}]}], \"cpeApplicability\": [{\"nodes\": [{\"operator\": \"OR\", \"negate\": false, \"cpeMatch\": [{\"vulnerable\": true, \"criteria\": \"cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:*\", \"versionEndExcluding\": \"3.10.3\"}]}]}], \"metrics\": [{\"format\": \"CVSS\", \"cvssV4_0\": {\"version\": \"4.0\", \"vectorString\": \"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N\", \"attackVector\": \"NETWORK\", \"attackComplexity\": \"LOW\", \"attackRequirements\": \"NONE\", \"privilegesRequired\": \"NONE\", \"userInteraction\": \"NONE\", \"vulnConfidentialityImpact\": \"NONE\", \"vulnIntegrityImpact\": \"NONE\", \"vulnAvailabilityImpact\": \"LOW\", \"subConfidentialityImpact\": \"NONE\", \"subIntegrityImpact\": \"NONE\", \"subAvailabilityImpact\": \"NONE\", \"baseScore\": 6.9, \"baseSeverity\": \"MEDIUM\"}}, {\"format\": \"CVSS\", \"cvssV3_1\": {\"version\": \"3.1\", \"vectorString\": \"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L\", \"attackVector\": \"NETWORK\", \"attackComplexity\": \"LOW\", \"privilegesRequired\": \"NONE\", \"userInteraction\": \"NONE\", \"scope\": \"UNCHANGED\", \"confidentialityImpact\": \"NONE\", \"integrityImpact\": \"NONE\", \"availabilityImpact\": \"LOW\", \"baseScore\": 5.3, \"baseSeverity\": \"MEDIUM\"}}], \"references\": [{\"url\": \"https://github.com/nltk/nltk/security/advisories/GHSA-cw6x-m8jw-qmrh\", \"tags\": [\"vendor-advisory\"], \"name\": \"GitHub Security Advisory (GHSA-cw6x-m8jw-qmrh)\"}, {\"name\": \"VulnCheck Advisory: NLTK before 3.10.3 Denial of Service via Uncontrolled Recursion\", \"tags\": [\"third-party-advisory\"], \"url\": \"https://www.vulncheck.com/advisories/nltk-before-3.10.3-denial-of-service-via-uncontrolled-recursion\"}], \"credits\": [{\"lang\": \"en\", \"value\": \"JoshgunAbdullayev\", \"type\": \"reporter\"}], \"x_generator\": {\"engine\": \"vulncheck-endgame\"}}, \"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-81724\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"poc\"}, {\"Automatable\": \"yes\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-08-27T18:28:30.462220Z\"}}}], \"references\": [{\"url\": \"https://github.com/nltk/nltk/security/advisories/GHSA-cw6x-m8jw-qmrh\", \"tags\": [\"exploit\"]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-08-27T18:28:39.837Z\"}}]}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-81724\", \"assignerOrgId\": \"83251b91-4cc7-4094-a5c7-464a1b83ea10\", \"state\": \"PUBLISHED\", \"assignerShortName\": \"VulnCheck\", \"dateReserved\": \"2026-08-27T11:15:29.420Z\", \"datePublished\": \"2026-08-27T14:51:17.358Z\", \"dateUpdated\": \"2026-08-27T18:29:04.021Z\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.


Loading…

Loading…

Loading…

Sightings

Author Source Type Date

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
  • Confirmed: The vulnerability is confirmed from an analyst perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
  • Patched: This vulnerability was successfully patched by the user reporting the sighting.
  • Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
  • Not confirmed: The user expresses doubt about the veracity of the vulnerability.
  • Not patched: This vulnerability was not successfully patched by the user reporting the sighting.


Loading…

Loading…