CVE-2026-12372

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 v3 3.7 LOW

3.7^/10

CVSS v3 : LOW

Vector : AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Exploitability : 2.2 / Impact : 1.4

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction NONE

Confidentiality Impact LOW

Integrity Impact NONE

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://huntr.com/bounties/2911b643-571c-42e4-b0c2-9a1fa6f491db	Permissions Required
https://huntr.com/bounties/2911b643-571c-42e4-b0c2-9a1fa6f491db	Permissions Required

Configurations

Configuration 1 (hide)

cpe:2.3:a:nltk:nltk:3.9.4:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-08-09 23:16

Updated : 2026-09-04 13:59

NVD link : CVE-2026-12372

Mitre link : CVE-2026-12372

CVE.ORG link : CVE-2026-12372

JSON object : View

Products Affected

nltk

nltk

CWE

CWE-918

Server-Side Request Forgery (SSRF)

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