CVE-2026-12372

LowCVSS 3.7

Published: 09/08/2026(UTC)Updated: 12/08/2026(UTC)Translated: 10/08/2026(UTC)NVD NIST

Exploitation Probability (EPSS)

Low risk

0.26%

18th percentile - higher than 18% of all known CVEs

Summary

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.

Risk Assessment

An attacker can exploit SSRF to send requests to internal resources in the shared address space, potentially exposing non-public services and data.

Recommendation

Update NLTK to a patched version or manually extend IP validation to include the 100.64.0.0/10 block. Restrict the ability to influence URLs passed to NLTK.

Original NVD description (English source)

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.