CVE-2025-71408 (GCVE-0-2025-71408)

Vulnerability from cvelistv5 – Published: 2026-07-24 21:07 – Updated: 2026-10-08 15:21 X_Open Source
VLAI
Title
NLTK < 3.9.3 Eval Injection via collocations.py Command-Line Arguments
Summary
NLTK (Natural Language Toolkit) before version 3.9.3 contains an eval injection vulnerability in the nltk.collocations module that allows an attacker who controls command-line arguments to execute arbitrary Python code. When collocations.py is invoked directly, the __main__ block passes command-line arguments directly to eval() as suffixes of BigramAssocMeasures without allowlist validation or sanitization, enabling an attacker to supply a Python expression that escapes the intended attribute lookup and executes arbitrary code including OS commands via the os module.
Severity
8.5 (High)
CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: poc Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-07-27 17:22 UTC
CWE
  • CWE-95 - Improper Neutralization of Directives in Dynamically Evaluated Code ('Eval Injection')
Assigner
VulnCheck CNA under the mitre root
CNA scorecard B 84/100 over 6182 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
ntlk ntlk Affected: 0 , < 3.9.3 (semver)
guessed Create a notification for this product.
Date Public
2025-11-17 00:00
Credits
Yunus AYDIN
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2025-71408",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-07-27T17:22:32.579274Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-07-27T17:22:48.131Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "affected",
          "packageURL": "pkg:pypi/nltk",
          "product": "ntlk",
          "repo": "https://github.com/nltk/nltk",
          "vendor": "ntlk",
          "versions": [
            {
              "lessThan": "3.9.3",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Yunus AYDIN"
        }
      ],
      "datePublic": "2025-11-17T00:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "NLTK (Natural Language Toolkit) before version 3.9.3 contains an eval injection vulnerability in the nltk.collocations module that allows an attacker who controls command-line arguments to execute arbitrary Python code. When collocations.py is invoked directly, the __main__ block passes command-line arguments directly to eval() as suffixes of BigramAssocMeasures without allowlist validation or sanitization, enabling an attacker to supply a Python expression that escapes the intended attribute lookup and executes arbitrary code including OS commands via the os module."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "LOCAL",
            "baseScore": 8.5,
            "baseSeverity": "HIGH",
            "exploitMaturity": "NOT_DEFINED",
            "privilegesRequired": "LOW",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "HIGH",
            "vulnIntegrityImpact": "HIGH",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        },
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "LOCAL",
            "availabilityImpact": "HIGH",
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-95",
              "description": "Improper Neutralization of Directives in Dynamically Evaluated Code (\u0027Eval Injection\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-08T15:21:35.203Z",
        "orgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
        "shortName": "VulnCheck"
      },
      "references": [
        {
          "name": "Researcher Disclosure",
          "tags": [
            "technical-description",
            "exploit"
          ],
          "url": "https://aydinnyunus.github.io/2026/06/07/command-injection-nltk-collocations-eval/"
        },
        {
          "name": "NLTK 3.9.3 Release Notes",
          "tags": [
            "release-notes",
            "patch"
          ],
          "url": "https://github.com/nltk/nltk/releases/tag/3.9.3"
        },
        {
          "name": "Pull Request",
          "tags": [
            "issue-tracking",
            "patch"
          ],
          "url": "https://github.com/nltk/nltk/pull/3465"
        },
        {
          "name": "Patch Commit",
          "tags": [
            "patch"
          ],
          "url": "https://github.com/nltk/nltk/commit/66f14096d952ec8f04934f515e027534bd4eb0ac"
        },
        {
          "tags": [
            "third-party-advisory"
          ],
          "url": "https://www.vulncheck.com/advisories/nltk-eval-injection-via-collocations-py-command-line-arguments"
        }
      ],
      "source": {
        "discovery": "UNKNOWN"
      },
      "tags": [
        "x_open-source"
      ],
      "title": "NLTK \u003c 3.9.3 Eval Injection via collocations.py Command-Line Arguments",
      "x_generator": {
        "engine": "vulncheck"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
    "assignerShortName": "VulnCheck",
    "cveId": "CVE-2025-71408",
    "datePublished": "2026-07-24T21:07:49.610Z",
    "dateReserved": "2026-07-24T20:57:08.784Z",
    "dateUpdated": "2026-10-08T15:21:35.203Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2025-71408",
      "date": "2026-10-15",
      "epss": "0.00265",
      "percentile": "0.1717"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "defaultStatus": "affected",
                "packageURL": "pkg:pypi/nltk",
                "product": "ntlk",
                "repo": "https://github.com/nltk/nltk",
                "vendor": "ntlk",
                "versions": [
                  {
                    "lessThan": "3.9.3",
                    "status": "affected",
                    "version": "0",
                    "versionType": "semver"
                  }
                ]
              }
            ],
            "source": "disclosure@vulncheck.com"
          }
        ],
        "configurations": [
          {
            "nodes": [
              {
                "cpeMatch": [
                  {
                    "criteria": "cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:*",
                    "matchCriteriaId": "22061B61-87EB-4006-8152-23CD3514C2AE",
                    "versionEndExcluding": "3.9.3",
                    "vulnerable": true
                  }
                ],
                "negate": false,
                "operator": "OR"
              }
            ]
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "NLTK (Natural Language Toolkit) before version 3.9.3 contains an eval injection vulnerability in the nltk.collocations module that allows an attacker who controls command-line arguments to execute arbitrary Python code. When collocations.py is invoked directly, the __main__ block passes command-line arguments directly to eval() as suffixes of BigramAssocMeasures without allowlist validation or sanitization, enabling an attacker to supply a Python expression that escapes the intended attribute lookup and executes arbitrary code including OS commands via the os module."
          },
          {
            "lang": "es",
            "value": "NLTK (Natural Language Toolkit) antes de la versi\u00f3n 3.9.3 contiene una vulnerabilidad de inyecci\u00f3n de eval en el m\u00f3dulo nltk.collocations que permite a un atacante que controla los argumentos de l\u00ednea de comandos ejecutar c\u00f3digo Python arbitrario. Cuando se invoca directamente collocations.py, el bloque __main__ pasa los argumentos de l\u00ednea de comandos directamente a eval() como sufijos de BigramAssocMeasures sin validaci\u00f3n de lista de permitidos ni saneamiento, lo que permite a un atacante suministrar una expresi\u00f3n Python que evade la b\u00fasqueda de atributo prevista y ejecuta c\u00f3digo arbitrario, incluyendo comandos del sistema operativo a trav\u00e9s del m\u00f3dulo os."
          }
        ],
        "id": "CVE-2025-71408",
        "lastModified": "2026-10-08T16:16:53.740",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 1.8,
              "impactScore": 5.9,
              "source": "disclosure@vulncheck.com",
              "type": "Secondary"
            }
          ],
          "cvssMetricV40": [
            {
              "cvssData": {
                "Automatable": "NOT_DEFINED",
                "Recovery": "NOT_DEFINED",
                "Safety": "NOT_DEFINED",
                "attackComplexity": "LOW",
                "attackRequirements": "NONE",
                "attackVector": "LOCAL",
                "availabilityRequirement": "NOT_DEFINED",
                "baseScore": 8.5,
                "baseSeverity": "HIGH",
                "confidentialityRequirement": "NOT_DEFINED",
                "exploitMaturity": "NOT_DEFINED",
                "integrityRequirement": "NOT_DEFINED",
                "modifiedAttackComplexity": "NOT_DEFINED",
                "modifiedAttackRequirements": "NOT_DEFINED",
                "modifiedAttackVector": "NOT_DEFINED",
                "modifiedPrivilegesRequired": "NOT_DEFINED",
                "modifiedSubAvailabilityImpact": "NOT_DEFINED",
                "modifiedSubConfidentialityImpact": "NOT_DEFINED",
                "modifiedSubIntegrityImpact": "NOT_DEFINED",
                "modifiedUserInteraction": "NOT_DEFINED",
                "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
                "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
                "modifiedVulnIntegrityImpact": "NOT_DEFINED",
                "privilegesRequired": "LOW",
                "providerUrgency": "NOT_DEFINED",
                "subAvailabilityImpact": "NONE",
                "subConfidentialityImpact": "NONE",
                "subIntegrityImpact": "NONE",
                "userInteraction": "NONE",
                "valueDensity": "NOT_DEFINED",
                "vectorString": "CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
                "version": "4.0",
                "vulnAvailabilityImpact": "HIGH",
                "vulnConfidentialityImpact": "HIGH",
                "vulnIntegrityImpact": "HIGH",
                "vulnerabilityResponseEffort": "NOT_DEFINED"
              },
              "source": "disclosure@vulncheck.com",
              "type": "Secondary"
            }
          ],
          "ssvcV203": [
            {
              "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "ssvcData": {
                "id": "CVE-2025-71408",
                "options": [
                  {
                    "exploitation": "poc"
                  },
                  {
                    "automatable": "no"
                  },
                  {
                    "technicalImpact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-07-27T17:22:32.579274Z",
                "version": "2.0.3"
              }
            }
          ]
        },
        "published": "2026-07-24T22:16:50.063",
        "references": [
          {
            "source": "disclosure@vulncheck.com",
            "tags": [
              "Exploit",
              "Press/Media Coverage",
              "Third Party Advisory"
            ],
            "url": "https://aydinnyunus.github.io/2026/06/07/command-injection-nltk-collocations-eval/"
          },
          {
            "source": "disclosure@vulncheck.com",
            "tags": [
              "Patch"
            ],
            "url": "https://github.com/nltk/nltk/commit/66f14096d952ec8f04934f515e027534bd4eb0ac"
          },
          {
            "source": "disclosure@vulncheck.com",
            "tags": [
              "Issue Tracking",
              "Patch"
            ],
            "url": "https://github.com/nltk/nltk/pull/3465"
          },
          {
            "source": "disclosure@vulncheck.com",
            "tags": [
              "Release Notes"
            ],
            "url": "https://github.com/nltk/nltk/releases/tag/3.9.3"
          },
          {
            "source": "disclosure@vulncheck.com",
            "tags": [
              "Patch",
              "Third Party Advisory"
            ],
            "url": "https://www.vulncheck.com/advisories/nltk-eval-injection-via-collocations-py-command-line-arguments"
          }
        ],
        "sourceIdentifier": "disclosure@vulncheck.com",
        "vulnStatus": "Analyzed",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-95"
              }
            ],
            "source": "disclosure@vulncheck.com",
            "type": "Secondary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-10-15T10:42:32+00:00",
      "cve": "CVE-2025-71408",
      "id": "CVE-2025-71408",
      "initial_release_date": "2025-01-01T00:00:00+00:00",
      "product_status:fixed": "2",
      "product_status:known_affected": "3",
      "product_status:known_not_affected": "244",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "nltk: NLTK: Arbitrary Code Execution via Eval Injection in Collocations Module",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-71408.json",
      "version": "3"
    },
    "vulnrichment": {
      "containers": {
        "adp": [
          {
            "metrics": [
              {
                "other": {
                  "content": {
                    "id": "CVE-2025-71408",
                    "options": [
                      {
                        "Exploitation": "poc"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "total"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2026-07-27T17:22:32.579274Z",
                    "version": "2.0.3"
                  },
                  "type": "ssvc"
                }
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2026-07-27T17:22:42.530Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
              "defaultStatus": "affected",
              "packageURL": "pkg:pypi/nltk",
              "product": "ntlk",
              "repo": "https://github.com/nltk/nltk",
              "vendor": "ntlk",
              "versions": [
                {
                  "lessThan": "3.9.3",
                  "status": "affected",
                  "version": "0",
                  "versionType": "semver"
                }
              ]
            }
          ],
          "credits": [
            {
              "lang": "en",
              "type": "finder",
              "value": "Yunus AYDIN"
            }
          ],
          "datePublic": "2025-11-17T00:00:00.000Z",
          "descriptions": [
            {
              "lang": "en",
              "value": "NLTK (Natural Language Toolkit) before version 3.9.3 contains an eval injection vulnerability in the nltk.collocations module that allows an attacker who controls command-line arguments to execute arbitrary Python code. When collocations.py is invoked directly, the __main__ block passes command-line arguments directly to eval() as suffixes of BigramAssocMeasures without allowlist validation or sanitization, enabling an attacker to supply a Python expression that escapes the intended attribute lookup and executes arbitrary code including OS commands via the os module."
            }
          ],
          "metrics": [
            {
              "cvssV4_0": {
                "Automatable": "NOT_DEFINED",
                "Recovery": "NOT_DEFINED",
                "Safety": "NOT_DEFINED",
                "attackComplexity": "LOW",
                "attackRequirements": "NONE",
                "attackVector": "LOCAL",
                "baseScore": 8.5,
                "baseSeverity": "HIGH",
                "exploitMaturity": "NOT_DEFINED",
                "privilegesRequired": "LOW",
                "providerUrgency": "NOT_DEFINED",
                "subAvailabilityImpact": "NONE",
                "subConfidentialityImpact": "NONE",
                "subIntegrityImpact": "NONE",
                "userInteraction": "NONE",
                "valueDensity": "NOT_DEFINED",
                "vectorString": "CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
                "version": "4.0",
                "vulnAvailabilityImpact": "HIGH",
                "vulnConfidentialityImpact": "HIGH",
                "vulnIntegrityImpact": "HIGH",
                "vulnerabilityResponseEffort": "NOT_DEFINED"
              },
              "format": "CVSS",
              "scenarios": [
                {
                  "lang": "en",
                  "value": "GENERAL"
                }
              ]
            },
            {
              "cvssV3_1": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "format": "CVSS",
              "scenarios": [
                {
                  "lang": "en",
                  "value": "GENERAL"
                }
              ]
            }
          ],
          "problemTypes": [
            {
              "descriptions": [
                {
                  "cweId": "CWE-95",
                  "description": "Improper Neutralization of Directives in Dynamically Evaluated Code (\u0027Eval Injection\u0027)",
                  "lang": "en",
                  "type": "CWE"
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-10-08T15:21:35.203Z",
            "orgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
            "shortName": "VulnCheck"
          },
          "references": [
            {
              "name": "Researcher Disclosure",
              "tags": [
                "technical-description",
                "exploit"
              ],
              "url": "https://aydinnyunus.github.io/2026/06/07/command-injection-nltk-collocations-eval/"
            },
            {
              "name": "NLTK 3.9.3 Release Notes",
              "tags": [
                "release-notes",
                "patch"
              ],
              "url": "https://github.com/nltk/nltk/releases/tag/3.9.3"
            },
            {
              "name": "Pull Request",
              "tags": [
                "issue-tracking",
                "patch"
              ],
              "url": "https://github.com/nltk/nltk/pull/3465"
            },
            {
              "name": "Patch Commit",
              "tags": [
                "patch"
              ],
              "url": "https://github.com/nltk/nltk/commit/66f14096d952ec8f04934f515e027534bd4eb0ac"
            },
            {
              "tags": [
                "third-party-advisory"
              ],
              "url": "https://www.vulncheck.com/advisories/nltk-eval-injection-via-collocations-py-command-line-arguments"
            }
          ],
          "source": {
            "discovery": "UNKNOWN"
          },
          "tags": [
            "x_open-source"
          ],
          "title": "NLTK \u003c 3.9.3 Eval Injection via collocations.py Command-Line Arguments",
          "x_generator": {
            "engine": "vulncheck"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
        "assignerShortName": "VulnCheck",
        "cveId": "CVE-2025-71408",
        "datePublished": "2026-07-24T21:07:49.610Z",
        "dateReserved": "2026-07-24T20:57:08.784Z",
        "dateUpdated": "2026-10-08T15:21:35.203Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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.