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High

NLTK (Natural Language Toolkit) before version 3.9.3 contains an eval injection vulnerability in the nltk.collocations module that allows an attacker who controls command-line arguments to execute arb

  • Disclosed: 24.07.2026
  • Updated: 11.10.2026 14:19

NLTK (Natural Language Toolkit) before version 3.9.3 contains an eval injection vulnerability in the nltk.collocations module that allows an attacker who controls command-line arguments to execute arbitrary Python code. When collocations.py is invoked directly, the main block passes command-line arguments directly to eval() as suffixes of BigramAssocMeasures without allowlist validation or sanitization, enabling an attacker to supply a Python expression that escapes the intended attribute lookup and executes arbitrary code including OS commands via the os module.

Affected software

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PlatformPackageVulnerable versionsFixed in
Python (PyPI) nltk < 3.9.3 3.9.3

References

CVSS score -
CVSS vector
CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/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
Weakness (CWE)
CWE-95
Platform
Python (PyPI)
Package
nltk
Disclosed
24.07.2026
Updated
11.10.2026 14:19

Sources and licenses

OSV / GitHub Advisory Database - GHSA-848c-c2cx-j7qx - CC BY 4.0

OSV / GitHub Advisory Database - PYSEC-2026-3657 - PyPA Advisory Database; CC BY 4.0

Vulnerability history: nltk

All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.

All (52) in the archive
Total entries
52
First → latest
08.2019 09.2026
Without a fix
6
Exploited in attacks
0

Severity breakdown

  • Critical 5
  • High 32
  • Medium 13
  • Low 2

Disclosures per year

Severity:
  1. NLTK (Natural Language Toolkit) before version 3.9.3 contains an eval injection vulnerability in the nltk.collocations module that allows an attacker who controls command-line arguments to execute arb this entry
    High CVE-2025-71408 < 3.9.3 3.9.3
  2. NLTK: Uncontrolled search path when invoking the Graphviz 'dot' binary
    High · 7.8 CVE-2026-78680 < 3.10.3 3.10.3
  3. NLTK: Model-artifact APIs bypass pathsec and touch files outside allowed roots
    High · 7.0 CVE-2026-81726 <= 3.10.3 no fix
  4. NLTK: ReDoS in nltk.tgrep via unvalidated user-supplied regular expressions
    High CVE-2026-80206 < 3.10.3 3.10.3
  5. NLTK: ReDoS in nltk.text.Text.findall() via unvalidated user-supplied regular expressions
    High · 7.5 CVE-2026-80205 < 3.10.0 3.10.0
  6. NLTK: JVM argument injection bypass via per-call options in the NLTK Stanford wrappers (incomplete fix of CVE-2026-12841)
    Critical · 9.8 CVE-2026-79675 < 3.10.3 3.10.3
  7. NLTK: Corpus readers follow symlinks outside trusted roots despite pathsec enforcement
    High CVE-2026-79676 < 3.10.3 3.10.3
  8. NLTK: Corpus Reader Sandbox Bypass
    High CVE-2026-79674 < 3.10.3 3.10.3
  9. NLTK: Allowlisted pickle loaders still permit code execution in current source
    Critical CVE-2026-79657 < 3.10.3 3.10.3
  10. NLTK: Unsafe Pickle Deserialization in TransitionParser Allows Remote Code Execution
    Critical CVE-2026-78683 < 3.10.0 3.10.0
  11. NLTK: Entity-expansion DoS (billion laughs) via remaining raw ElementTree parses
    High CVE-2026-78681 < 3.10.3 3.10.3
  12. NLTK: pathsec SSRF protection can be bypassed when a proxy is configured
    High CVE-2026-78682 < 3.10.3 3.10.3
  13. NLTK AllowlistUnpickler dotted-name validation bypass allows remote code execution
    High · 8.8 CVE-2026-71513 >= 3.10.0, < 3.10.3 3.10.3
  14. NLTK: Symlink escape in CorpusReader allows arbitrary local file read outside the corpus root
    High · 6.2 CVE-2026-70626 < 3.9.4 3.9.4
  15. NLTK: StreamBackedCorpusView Bypasses pathsec.ENFORCE - Arbitrary Local File Read
    High CVE-2026-63312 < 3.10.0 3.10.0
  16. NLTK: Symlink-based sandbox bypass in FramenetCorpusReader (bypasses the fix for CVE-2026-54292)
    High · 7.5 CVE-2026-62384 >= 3.10.0, < 3.10.2 3.10.2
  17. NLTK: Stable FrameNet and NKJP readers parse outside-root XML
    High · 5.9 CVE-2026-62385 < 3.10.0 3.10.0
  18. NLTK: Default ENFORCE=False Disables All pathsec Security Controls
    High CVE-2026-62388 < 3.10.0 3.10.0
  19. NLTK TweetTokenizer vulnerable to denial of service through catastrophic regex backtracking
    High · 7.5 CVE-2026-72818 < 3.10.1 3.10.1
  20. Natural Language Toolkit (NLTK): DNS-rebinding SSRF filter bypass in nltk.pathsec.urlopen (nltk.download / nltk.data.load) defeats ENFORCE mode
    High · 8.6 CVE-2026-12075 < 3.10.0 3.10.0
  21. Natural Language Toolkit (NLTK): ReDoS in NLTK ReviewsCorpusReader FEATURES regex
    High · 7.5 CVE-2026-12061 < 3.10.0 3.10.0
Show more (16) Showing 21 of 37

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