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NLTK: Uncontrolled search path when invoking the Graphviz 'dot' binary

  • Veröffentlicht: 01.09.2026
  • Aktualisiert: 11.10.2026 15:18

Two NLTK sites executed the Graphviz dot program by bare name, so process creation resolved it via the search path — and on Windows via the current working directory — rather than a validated absolute location. An attacker who can place a file named dot where resolution looks (the CWD on Windows, or a writable/relative entry such as . on PATH) has their binary executed in place of Graphviz (arbitrary code execution).

Affected (<= 3.10.2):

  • nltk.parse.dependencygraph.dot2img — called find_binary("dot") but discarded the returned validated path and then ran the bare name ["dot", ...], so the validation had no effect.
  • nltk.translate.api.AlignedSent._repr_svg_ — ran the bare name with no validation at all (IPython SVG rendering).

This is the same class already fixed for the senna, weka, boxer, malt, repp and hunpos wrappers. nltk.internals.find_binary refuses a CWD-relative match for a bare tool name and returns only a trusted absolute path; the fix runs that path in both sites.

Attack demonstration

Captured output, not illustrative. A ./dot that writes a PWNED marker, planted in the CWD with . prepended to PATH.

The vulnerable behaviour (old bare-name exec):

Control (OLD behavior) — bare ['dot'] in this dir with '.' on PATH:
  bare ['dot'] executed planted binary = True

The patched functions refuse it:

FIXED code, with ./dot planted and '.' on PATH:
  dependencygraph.dot2img : Exception "Cannot find the dot binary..."  | planted-binary-executed=False  safe
  AlignedSent._repr_svg_  : Exception "Cannot find the dot binary..."  | planted-binary-executed=False  safe

And find_binary itself was attacked directly (the fix trusts nothing else):

Attack 1: ./dot in CWD, no dot on PATH            -> LookupError (refused)  safe
Attack 2: ./dot/dot (dir 'dot' holding 'dot')     -> LookupError (refused)  safe
Attack 3: '.' on PATH + ./dot                     -> LookupError (refused)  safe
Attack 4: attacker-writable ABSOLUTE dir on PATH  -> returned /…/evilbin/dot (absolute)

Attack 4 is out of scope: trusting an absolute directory that is already on PATH is the operating system's own trust model — an attacker who can write to a PATH directory owns the account regardless of NLTK. find_binary defends specifically against the CWD/relative injection that bare-name exec is vulnerable to (attacks 1–3), which is exactly what this fix inherits.

Environment: python 3.13.7. dot is not required to reproduce — the planted binary is the payload.

Betroffene Software

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PlattformPaketAnfällige VersionenBehoben in
Python (PyPI) nltk < 3.10.3 3.10.3

Verweise

CVSS-Wert 7.8/10
CVSS-Vektor
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Schwäche (CWE)
CWE-426, CWE-427
Plattform
Python (PyPI)
Paket
nltk
Veröffentlicht
01.09.2026
Aktualisiert
11.10.2026 15:18

Quellen und Lizenzen

OSV / GitHub Advisory Database - PYSEC-2026-3868 - PyPA Advisory Database; CC BY 4.0

OSV / GitHub Advisory Database - GHSA-6hwm-xvph-95vm - CC BY 4.0

Schwachstellenhistorie: nltk

Alle veröffentlichten Schwachstellen dieses Pakets (Python (PyPI)), neueste zuerst. Zeigt, ob es ein einmaliger Ausrutscher ist oder ein Paket, das man im Auge behalten muss.

Alle (52) im Archiv
Einträge insgesamt
52
Erste → letzte
08.2019 09.2026
Ohne Fix
6
In Angriffen ausgenutzt
0

Verteilung nach Schweregrad

  • Kritisch 5
  • Hoch 32
  • Mittel 13
  • Niedrig 2

Veröffentlichungen pro Jahr

Schweregrad:
  1. NLTK: Uncontrolled search path when invoking the Graphviz 'dot' binary dieser Eintrag
    Hoch · 7.8 CVE-2026-78680 < 3.10.3 3.10.3
  2. NLTK: Model-artifact APIs bypass pathsec and touch files outside allowed roots
    Hoch · 7.0 CVE-2026-81726 <= 3.10.3 keine Korrektur
  3. NLTK: ReDoS in nltk.tgrep via unvalidated user-supplied regular expressions
    Hoch CVE-2026-80206 < 3.10.3 3.10.3
  4. NLTK: ReDoS in nltk.text.Text.findall() via unvalidated user-supplied regular expressions
    Hoch · 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)
    Kritisch · 9.8 CVE-2026-79675 < 3.10.3 3.10.3
  6. NLTK: Corpus readers follow symlinks outside trusted roots despite pathsec enforcement
    Hoch CVE-2026-79676 < 3.10.3 3.10.3
  7. NLTK: Corpus Reader Sandbox Bypass
    Hoch CVE-2026-79674 < 3.10.3 3.10.3
  8. NLTK: Allowlisted pickle loaders still permit code execution in current source
    Kritisch CVE-2026-79657 < 3.10.3 3.10.3
  9. NLTK: Unsafe Pickle Deserialization in TransitionParser Allows Remote Code Execution
    Kritisch CVE-2026-78683 < 3.10.0 3.10.0
  10. NLTK: Entity-expansion DoS (billion laughs) via remaining raw ElementTree parses
    Hoch CVE-2026-78681 < 3.10.3 3.10.3
  11. NLTK: pathsec SSRF protection can be bypassed when a proxy is configured
    Hoch CVE-2026-78682 < 3.10.3 3.10.3
  12. NLTK AllowlistUnpickler dotted-name validation bypass allows remote code execution
    Hoch · 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
    Hoch · 6.2 CVE-2026-70626 < 3.9.4 3.9.4
  14. NLTK: StreamBackedCorpusView Bypasses pathsec.ENFORCE - Arbitrary Local File Read
    Hoch CVE-2026-63312 < 3.10.0 3.10.0
  15. NLTK: Symlink-based sandbox bypass in FramenetCorpusReader (bypasses the fix for CVE-2026-54292)
    Hoch · 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
    Hoch · 5.9 CVE-2026-62385 < 3.10.0 3.10.0
  17. NLTK: Default ENFORCE=False Disables All pathsec Security Controls
    Hoch CVE-2026-62388 < 3.10.0 3.10.0
  18. NLTK TweetTokenizer vulnerable to denial of service through catastrophic regex backtracking
    Hoch · 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
    Hoch · 8.6 CVE-2026-12075 < 3.10.0 3.10.0
  20. Natural Language Toolkit (NLTK): ReDoS in NLTK ReviewsCorpusReader FEATURES regex
    Hoch · 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)
    Hoch · 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)
    Hoch · 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
    Hoch 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
    Hoch · 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
    Hoch · 7.5 CVE-2026-12243 <= 3.9.4 keine Korrektur
  26. Natural Language Toolkit (NLTK): URL-Encoded Path Traversal in nltk.data.load() Allows Arbitrary Local File Read
    Hoch · 7.5 CVE-2026-54293 < 3.10.0 3.10.0
  27. NLTK has a Downloader Path Traversal Vulnerability (AFO) - Arbitrary File Overwrite
    Hoch · 8.1 CVE-2026-33236 <= 3.9.2 keine Korrektur
  28. Unauthenticated remote shutdown in nltk.app.wordnet_app
    Hoch · 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
    Hoch · 7.5 CVE-2026-0846 <= 3.9.2 keine Korrektur
  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
    Kritisch · 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
    Hoch · 7.5 CVE-2026-0847 < 3.9.3 3.9.3
  32. NLTK has a Zip Slip Vulnerability
    Kritisch · 10.0 CVE-2025-14009 < 3.9.3 3.9.3
  33. ntlk unsafe deserialization vulnerability
    Hoch · 7.5 CVE-2024-39705 < 3.9 3.9
  34. NLTK Vulnerable to REDoS
    Hoch · 7.5 CVE-2021-3842 < 3.6.6 3.6.6
  35. Inefficient Regular Expression Complexity in nltk (word_tokenize, sent_tokenize)
    Hoch · 7.5 CVE-2021-43854 < 3.6.6 3.6.6
  36. NLTK Vulnerable to REDoS
    Hoch · 7.5 CVE-2021-3828 < 3.6.4 3.6.4
  37. NLTK Vulnerable To Path Traversal
    Hoch · 7.5 CVE-2019-14751 < 3.4.5 3.4.5

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