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CVE-2026-63311

NLTK before 3.10.0 SSRF via DNS Resolution Failure

Published: Aug 22, 2026Updated: Aug 22, 2026 Sources: CVE List NVDCWE-918
5.3MEDIUM
NVD MITRE
EPSS Score
0.2%
Top 84.0%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available
Self-Check
Not available

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).

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:NI:LA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:LIntegrity
Low
A:NAvailability
None
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Weaknesses

CWE-918

Affected Products

nltk
oss-projectaka nltk/nltk
nltkLibrary
AI / ML / ml-framework

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.

Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

2 techniques
Command and Control
Initial Access
View detailed technique mapping

References

https://github.com/nltk/nltk/security/advisories/GHSA-3gqm-fcw5-w839
github.com
https://www.vulncheck.com/advisories/nltk-before-ssrf-via-dns-resolution-failure
vulncheck.com

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