All vulnerabilities
CVE-2026-12372GHSA-2jhm-w3mp-jcwrPYSEC-2026-3955

NLTK network URL validation permits SSRF to RFC 6598 shared-address-space hosts

nltk nltkpipLibraries & packages
Open in ThreatlineRecord JSON
CVSS
3.7Low
ExploitationPublic exploit codeCISA's assessment says proof of concept code is public, assessed 12 Aug 2026. Not in the KEV catalogCISA via CVE List
Exploit odds (EPSS)0.26%Chance of exploitation activity in the next 30 days, higher than 16% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in3.10.0Fixed versionGitHub
Published9 Aug 2026Updated 2 Oct 2026CVE List

What fixes it

  • 3.10.0nltk, pipGitHub
  • 3.10.0nltk, PyPIOSVpip install "nltk>=3.10.0"

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

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.

Text from CVE List

Affected versions 53

  • nltk, pip< 3.10.0GitHub
  • nltk/nltkaffected: unspecified through latestCVE List
  • nltk, PyPIfrom first release, fixed in 3.10.0OSV
  • nltk, PyPI0.8OSV
  • nltk, PyPI0.9OSV
  • nltk, PyPI0.9.3OSV
  • nltk, PyPI0.9.4OSV
  • nltk, PyPI0.9.5OSV
  • nltk, PyPI0.9.6OSV
  • nltk, PyPI0.9.7OSV
  • nltk, PyPI0.9.8OSV
  • nltk, PyPI0.9.9OSV
  • nltk, PyPI2.0.1OSV
  • nltk, PyPI2.0.1rc1OSV
  • nltk, PyPI2.0.1rc2-gitOSV
  • nltk, PyPI2.0.1rc3OSV
  • nltk, PyPI2.0.1rc4OSV
  • nltk, PyPI2.0.2OSV
  • nltk, PyPI2.0.3OSV
  • nltk, PyPI2.0.4OSV
  • nltk, PyPI2.0.5OSV
  • nltk, PyPI2.0b4OSV
  • nltk, PyPI2.0b5OSV
  • nltk, PyPI2.0b6OSV
  • nltk, PyPI2.0b7OSV
  • nltk, PyPI2.0b8OSV
  • nltk, PyPI2.0b9OSV
  • nltk, PyPI3.0.0OSV
  • nltk, PyPI3.0.0b1OSV
  • nltk, PyPI3.0.0b2OSV
  • nltk, PyPI3.0.1OSV
  • nltk, PyPI3.0.2OSV
  • nltk, PyPI3.0.3OSV
  • nltk, PyPI3.0.4OSV
  • nltk, PyPI3.0.5OSV
  • nltk, PyPI3.1OSV
  • nltk, PyPI3.2OSV
  • nltk, PyPI3.2.1OSV
  • nltk, PyPI3.2.2OSV
  • nltk, PyPI3.2.3OSV
  • nltk, PyPI3.2.4OSV
  • nltk, PyPI3.2.5OSV
  • nltk, PyPI3.3OSV
  • nltk, PyPI3.4OSV
  • nltk, PyPI3.4.1OSV
  • nltk, PyPI3.4.2OSV
  • nltk, PyPI3.4.3OSV
  • nltk, PyPI3.4.4OSV
  • nltk, PyPI3.4.5OSV
  • nltk, PyPI3.5OSV
  • nltk, PyPI3.5b1OSV
  • nltk, PyPI3.6OSV
  • nltk, PyPI3.6.1OSV

References 6