Vulnerability · Published Aug 9, 2026 · Assigned by @huntr_ai
CVE-2026-12372Server-Side Request Forgery (SSRF) in nltk/nltk
Low 3.7
In plain English
A low-severity server-side request forgery in nltk/nltk from nltk. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 18% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | nltk | no fix listed | DEBIAN-CVE-2026-12372 |
| Debian:13 | nltk | no fix listed | DEBIAN-CVE-2026-12372 |
| Debian:14 | nltk | no fix listed | DEBIAN-CVE-2026-12372 |
| PyPI | nltk | 3.10.0 | GHSA-2jhm-w3mp-jcwr |
| PyPI | nltk | no fix listed | PYSEC-2026-3955 |
| Ubuntu:26.10 | nltk | no fix listed | UBUNTU-CVE-2026-12372 |
Affected products (as reported)
Weakness: CWE-918 · Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N