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HIGH

CVE-2026-63310

CVE-2026-63310 — NLTK before 3.9.3 Missing Post-Download Integrity Verification

NLTK before 3.9.3 fails to verify file integrity after downloading packages and before extraction in the downloader module. Attackers can perform man-in-the-middle attacks or DNS poisoning to inject malicious package contents that are extracted without validation.

Published Updated Sources: cvelistV5, VulnCheck

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Unreported

no source claims exploitation

EPSS

0%

chance of exploitation in 30 days

Affects

nltk

nltk

CVSS base

7.1

HIGH

CISA SSVC assessment

Three decision points CISA publishes for the CVEs it assesses · SSVC 2.0.3. A stakeholder decision, not a severity score.

CISA

Exploitation

PoC

none · proof-of-concept · active

Automatable

No

can an attacker script all four kill-chain steps

Technical impact

Total

partial · total control of the vulnerable component

Affected scope

The catalog records vendors and products as separate lists, not pairs, so which product belongs to which vendor is not something this page can say.

Vendors (1)

nltk

Products (1)

nltk

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactSource
7.1CVSS 3.1HIGH——cvelistV5

Weakness & attack patterns

  • CWE-494

Attack patterns reported against this CVE. The ATT&CK techniques below are inferred from its weakness class.

  • T1195.002Supply Chain Compromise: Compromise Software Supply Chain
  • T1072Software Deployment Tools
  • T1195.001Supply Chain Compromise: Software Dependencies and Development Tools

References

2 on the record

Elsewhere on this site

  • nltkevery CVE for this vendor
  • CWE-494other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.