SEPTEMBER 18, 2026
Live Feed
Back to database
Case File

CVE-2026-63311

MEDIUM · CVSS 5.3 EPSS 0.24% Public Exploit

Source: NVD + CISA KEV + EPSS · Published 2026-08-22 · Last synced 2026-09-18

CyberRota Analysis

AI-Generated

NLTK versions prior to 3.10.0 are vulnerable to a server-side request forgery (SSRF) due to inadequate validation in the validate_network_url() function, which fails to properly handle DNS resolution errors. This flaw allows attackers to exploit DNS resolution failures or DNS rebinding to access restricted network resources, including sensitive cloud metadata endpoints. Organizations using affected versions of NLTK should prioritize patching to mitigate the risk of unauthorized access to internal systems.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

GitHub PoC Links

Note: these links are listed for security research and verification purposes only.

CVE
CVE-2026-63311
Severity
MEDIUM
CVSS
5.3
EPSS
0.24%

Original NVD Description

NLTK before 3.10.0 (affected versions <= 3.9.4) contains a server-side request forgery (SSRF) vulnerability in the validate_network_url() function in nltk/pathsec.py. The _resolve_hostname() helper catches OSError and ValueError during socket.getaddrinfo() and returns an empty list; when DNS resolution fails, the validation loop executes no IP checks and the function fails open, allowing urlopen() to proceed without validation. An attacker who can trigger DNS resolution failures or use DNS rebinding can bypass SSRF protections and reach restricted network resources, including cloud metadata endpoints (e.g., 169.254.169.254).

Related CVEs

Other vulnerabilities affecting the same vendor(s)