{"cve":"CVE-2026-12372","nvd":{"published":"2026-08-09T23:16:35.793","modified":"2026-10-23T20:10:00.160","status":"Analyzed","description":"A Server-Side Request Forgery (SSRF) vulnerability exists in nltk/nltk versions 3.9.4 and the current develop branch. The `nltk.pathsec.validate_network_url()` function, intended to prevent SSRF by rejecting internal network addresses, fails to reject IPs in the RFC 6598 shared address space (`100.64.0.0/10`). This occurs because Python's `ipaddress` module does not classify such addresses as `is_private` or `is_global`, and the current guard only checks `is_private` and a few explicit categories. An attacker who can influence a URL passed to NLTK's network-loading helpers can exploit this vulnerability to make a strict-mode application send requests to shared-address-space hosts, potentially exposing non-public infrastructure reachable from the application host. The impact is limited to SSRF-style confidentiality exposure, with no code execution claimed.","cvss_v4":null,"cvss_v3":{"version":"3.0","vector":"CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","score":3.7},"cwes":["CWE-918"],"references":["https://huntr.com/bounties/2911b643-571c-42e4-b0c2-9a1fa6f491db","https://huntr.com/bounties/2911b643-571c-42e4-b0c2-9a1fa6f491db"],"products":["nltk:nltk"],"source":"nvd","synced_at":"2026-10-24T16:53:34.184483516+00:00"},"epss":{"cve":"CVE-2026-12372","score":0.0026,"percentile":0.17515,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-2jhm-w3mp-jcwr","url":"https://osv.dev/vulnerability/GHSA-2jhm-w3mp-jcwr","summary":"NLTK network URL validation permits SSRF to RFC 6598 shared-address-space hosts","modified":"2026-10-02T23:40:41.750758387Z","packages":[{"ecosystem":"PyPI","name":"nltk","purl":"pkg:pypi/nltk","ranges":["<3.10.0"],"fixed":["3.10.0"]}]},{"id":"PYSEC-2026-3955","url":"https://osv.dev/vulnerability/PYSEC-2026-3955","summary":"","modified":"2026-10-15T14:45:08.355892144Z","packages":[{"ecosystem":"PyPI","name":"nltk","purl":"pkg:pypi/nltk","ranges":["<=3.9.4"],"fixed":[]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}