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GHSA-crp9-r7rq-c8cg

Duplicate Advisory: pathsec SSRF protection can be bypassed when a proxy is configured

High Withdrawn Sep 2, 2026 PyPI
Severity
0.0 / 10
High · CVSS 4.0
Exploit chance (EPSS)
—
No score published
Known exploited
No
Not in CISA's catalog
Weakness
CWE-918 Server-Side Request Forgery (SSRF)
Fix
None yet
No fixed version published

Description

Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-6ww7-3frv-cqxh. This link is maintained to preserve external references.

Original Description

NLTK before 3.10.3 contains a server-side request forgery vulnerability in nltk.pathsec.urlopen (and callers nltk.data.load, nltk.downloader.Downloader.index/download) when an HTTP proxy is configured. pathsec.urlopen validates the requested hostname locally, but proxy-handler inheritance disables the safe HTTP/HTTPS handlers so the actual fetch is performed by the proxy against a destination that is never re-validated. An attacker can supply a validated public URL that the proxy forwards to an internal loopback-only service, allowing disclosure of internal HTTP resources, loading of forged downloader indexes, and installation of attacker-chosen package content.

Affected versions

PyPI

PackageVulnerableFixed in
nltk
<= 3.10.2
No fix yet

How to fix

No fixed version has been published yet. Until one is, remove or replace the package, or turn off or isolate the affected feature. This page updates when a fix ships.

Severity breakdown

CVSS 4.0 0.0

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Attack vector
Network
Attack complexity
Low
Attack requirements
None
Privileges required
None
User interaction
None
Confidentiality (vulnerable system)
High
Integrity (vulnerable system)
None
Availability (vulnerable system)
None
Confidentiality (subsequent systems)
None
Integrity (subsequent systems)
None
Availability (subsequent systems)
None
Exploit maturity
Not defined
Scope
X

CVSS 3.1 7.5

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

Weakness

CWE-918: Server-Side Request Forgery (SSRF)

The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.

References

Timeline

  1. Published
  2. Withdrawn
  3. Last updated by the source
AdvisorySeverityWhy it's related
GHSA-j456-xh4h-cpf2
NLTK: WekaClassifier passes an unvalidated caller-controlled model path to the weka JVM, bypassing nltk.pathsec containment
High Also affects nltk
GHSA-ff5c-cp5c-9wjf
NLTK: Uncontrolled resource consumption in RecursiveDescentParser via ambiguous or left-recursive grammars
Medium Also affects nltk
GHSA-f794-5jv7-7672
NLTK: Downloader.download follows hardlinks and overwrites outside-root files
High Also affects nltk
GHSA-8mgp-746c-j5xp
NLTK: Model-artifact APIs bypass pathsec and touch files outside allowed roots
High Also affects nltk
GHSA-8mpw-7fpc-4gqj
NLTK: Pl196xCorpusReader has quadratic ReDoS on malformed TEI blocks
Low Also affects nltk
GHSA-cw6x-m8jw-qmrh
NLTK: Uncontrolled recursion in nltk.featstruct.FeatStructReader causes unhandled RecursionError (DoS) via deeply nested feature-structure input
Medium Also affects nltk
GHSA-vp2x-qp44-57v7
NLTK: Quadratic CPU Exhaustion in `XMLCorpusView._read_xml_fragment()`
Low Also affects nltk
GHSA-ww6m-cw3f-q94g
NLTK: Quadratic-time DoS in PorterStemmer via long runs of 'y'
High Also affects nltk
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