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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: Uncontrolled search path when invoking the Graphviz 'dot' binary
    High · 7.8 CVE-2026-78680 < 3.10.3 3.10.3
  2. NLTK: Model-artifact APIs bypass pathsec and touch files outside allowed roots
    High · 7.0 CVE-2026-81726 <= 3.10.3 no fix
  3. NLTK: ReDoS in nltk.tgrep via unvalidated user-supplied regular expressions
    High CVE-2026-80206 < 3.10.3 3.10.3
  4. 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
  5. 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
  6. NLTK: Corpus readers follow symlinks outside trusted roots despite pathsec enforcement
    High CVE-2026-79676 < 3.10.3 3.10.3
  7. NLTK: Corpus Reader Sandbox Bypass
    High CVE-2026-79674 < 3.10.3 3.10.3
  8. NLTK: Allowlisted pickle loaders still permit code execution in current source
    Critical CVE-2026-79657 < 3.10.3 3.10.3
  9. NLTK: Unsafe Pickle Deserialization in TransitionParser Allows Remote Code Execution
    Critical CVE-2026-78683 < 3.10.0 3.10.0
  10. NLTK: Entity-expansion DoS (billion laughs) via remaining raw ElementTree parses
    High CVE-2026-78681 < 3.10.3 3.10.3
  11. NLTK: pathsec SSRF protection can be bypassed when a proxy is configured
    High CVE-2026-78682 < 3.10.3 3.10.3
  12. 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
  13. 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
  14. NLTK: StreamBackedCorpusView Bypasses pathsec.ENFORCE - Arbitrary Local File Read
    High CVE-2026-63312 < 3.10.0 3.10.0
  15. 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
  16. NLTK: Stable FrameNet and NKJP readers parse outside-root XML
    High · 5.9 CVE-2026-62385 < 3.10.0 3.10.0
  17. NLTK: Default ENFORCE=False Disables All pathsec Security Controls
    High CVE-2026-62388 < 3.10.0 3.10.0
  18. NLTK TweetTokenizer vulnerable to denial of service through catastrophic regex backtracking
    High · 7.5 CVE-2026-72818 < 3.10.1 3.10.1
  19. 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
  20. Natural Language Toolkit (NLTK): ReDoS in NLTK ReviewsCorpusReader FEATURES regex
    High · 7.5 CVE-2026-12061 < 3.10.0 3.10.0
  21. Natural Language Toolkit (NLTK): Path Traversal in NKJPCorpusReader leads to Arbitrary File Read and bypasses the nltk.pathsec sandbox (ENFORCE=True)
    High · 7.5 CVE-2026-12072 < 3.10.0 3.10.0
  22. Natural Language Toolkit (NLTK) has path traversal in FramenetCorpusReader.frame() that allows arbitrary XML file read, bypassing the nltk.pathsec sandbox (ENFORCE=True)
    High · 7.5 CVE-2026-12074 < 3.10.0 3.10.0
  23. 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
  24. In nltk/nltk versions 3.9.3 and earlier, five Stanford interface classes (StanfordPOSTagger, StanfordNERTagger, StanfordParser, StanfordDependencyParser, and StanfordNeuralDependencyParser) are vulner
    High · 7.8 CVE-2026-12252 < 3.9.4 3.9.4
  25. NLTK version 3.9.4 is vulnerable to a path traversal attack due to an incomplete fix for GitHub Issue #3504. The `_UNSAFE_NO_PROTOCOL_RE` regex in `nltk/data.py` checks for literal `../` sequences but
    High · 7.5 CVE-2026-12243 <= 3.9.4 no fix
  26. Natural Language Toolkit (NLTK): URL-Encoded Path Traversal in nltk.data.load() Allows Arbitrary Local File Read
    High · 7.5 CVE-2026-54293 < 3.10.0 3.10.0
  27. NLTK has a Downloader Path Traversal Vulnerability (AFO) - Arbitrary File Overwrite
    High · 8.1 CVE-2026-33236 <= 3.9.2 no fix
  28. Unauthenticated remote shutdown in nltk.app.wordnet_app
    High · 7.5 CVE-2026-33231 < 3.9.4 3.9.4
  29. A vulnerability in the `filestring()` function of the `nltk.util` module in nltk version 3.9.2 allows arbitrary file read due to improper validation of input paths. The function directly opens files s
    High · 7.5 CVE-2026-0846 <= 3.9.2 no fix
  30. NLTK versions <=3.9.2 are vulnerable to arbitrary code execution due to improper input validation in the StanfordSegmenter module. The module dynamically loads external Java .jar files without verific
    Critical · 10.0 CVE-2026-0848 < 3.9.3 3.9.3
  31. A vulnerability in NLTK versions up to and including 3.9.2 allows arbitrary file read via path traversal in multiple CorpusReader classes, including WordListCorpusReader, TaggedCorpusReader, and Brack
    High · 7.5 CVE-2026-0847 < 3.9.3 3.9.3
  32. NLTK has a Zip Slip Vulnerability
    Critical · 10.0 CVE-2025-14009 < 3.9.3 3.9.3
  33. ntlk unsafe deserialization vulnerability
    High · 7.5 CVE-2024-39705 < 3.9 3.9
  34. NLTK Vulnerable to REDoS
    High · 7.5 CVE-2021-3842 < 3.6.6 3.6.6
  35. Inefficient Regular Expression Complexity in nltk (word_tokenize, sent_tokenize)
    High · 7.5 CVE-2021-43854 < 3.6.6 3.6.6
  36. NLTK Vulnerable to REDoS
    High · 7.5 CVE-2021-3828 < 3.6.4 3.6.4
  37. NLTK Vulnerable To Path Traversal
    High · 7.5 CVE-2019-14751 < 3.4.5 3.4.5

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