CVE-2026-12372
Description
A flaw was found in NLTK. A Server-Side Request Forgery (SSRF) vulnerability allows an attacker to influence a URL passed to NLTK's network-loading helpers. This occurs because the nltk.pathsec.validate_network_url() function fails to properly identify and reject IP addresses within the RFC 6598 shared address space (100.64.0.0/10). This could lead to the exposure of non-public infrastructure reachable from the application host, resulting in confidentiality exposure.
Statement
This is a Low impact Server-Side Request Forgery (SSRF) vulnerability in the NLTK library. Red Hat products that incorporate NLTK and process untrusted URLs via its network-loading functions may be vulnerable. An attacker could influence a URL to cause the application to send requests to RFC 6598 shared address space hosts, potentially exposing internal network information. This flaw is limited to confidentiality exposure and does not enable code execution.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 3.7 | N/A | 3.7 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | Low | N/A | Low |
| Integrity Impact | None | N/A | None |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
cve.org: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Application Data
Integrity
Technical Impact: Execute Unauthorized Code or Commands
Access Control
Technical Impact: Bypass Protection Mechanism
By providing URLs to unexpected hosts or ports, attackers can make it appear that the server is sending the request, possibly bypassing access controls such as firewalls that prevent the attackers from accessing the URLs directly. The server can be used as a proxy to conduct port scanning of hosts in internal networks, use other URLs such as that can access documents on the system (using file://), or use other protocols such as gopher:// or tftp://, which may provide greater control over the contents of requests.
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