{"schemaVersion":3,"id":"CVE-2026-12372","aliases":["GHSA-2jhm-w3mp-jcwr","PYSEC-2026-3955","UBUNTU-CVE-2026-12372","DEBIAN-CVE-2026-12372","openSUSE-SU-2026:11510-1"],"status":"published","duplicateOf":null,"title":null,"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.","dates":{"published":"2026-08-09T22:45:52.799Z","modified":"2026-08-12T17:48:54.679Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":3.7,"severity":"low","version":"3.0","versionLabel":"v3.0","source":"CVE.org","vector":"CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","computed":false,"selection":"backend-summary"},"metrics":[{"version":"3.0","versionLabel":"v3.0","source":"CVE.org","score":3.7,"severity":"low","vector":"CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","exploitability":null,"impact":null,"computed":false},{"version":"3.0","versionLabel":"v3.0","source":"OSV · Pypi","score":3.7,"severity":"low","vector":"CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","exploitability":5.6,"impact":2.3,"computed":true},{"version":"3.0","versionLabel":"v3.0","source":"OSV · 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