chore(deps): update dependency nltk to v3.10.3 [security]

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
nltk (source)	3.10.0 → 3.10.3

---

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

CVE-2026-78680 / GHSA-6hwm-xvph-95vm

More information

Details

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.

Severity

• CVSS Score: 8.5 / 10 (High)
• Vector String: 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

References

• https://github.com/nltk/nltk/security/advisories/GHSA-6hwm-xvph-95vm
• https://nvd.nist.gov/vuln/detail/CVE-2026-78680
• https://github.com/nltk/nltk/commit/1a3cd1764ab3deb084fb66d0ffb4873717659538
• https://github.com/nltk/nltk/releases/tag/v3.10.3
• https://www.vulncheck.com/advisories/nltk-before-arbitrary-code-execution-via-graphviz-dot-binary
• https://github.com/advisories/GHSA-6hwm-xvph-95vm

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

NLTK: JVM argument injection bypass via per-call options in the NLTK Stanford wrappers (incomplete fix of CVE-2026-12841)

CVE-2026-79675 / GHSA-m4rf-3fr8-xwx3

More information

Details

Vulnerability

The fix for CVE-2026-12841 (CWE-88, JVM argument injection) added _validate_java_options() to block dangerous JVM flags such as -agentlib, -agentpath, -javaagent, -Xrunjdwp, and @argfile references. However, the validation is only applied when setting global options via config_java(). The java() function's per-call options parameter -- added by PR #​3683 (CVE-2026-12615 fix) -- passes options directly to subprocess.Popen without calling _validate_java_options().

All four Stanford Java wrapper classes accept user-supplied java_options and route them through the unvalidated per-call path, bypassing the CVE-2026-12841 fix entirely.

Root Cause

In nltk/internals.py, the java() function (line 128) accepts an options keyword argument. When options is not None, it is converted to a list and prepended to the JVM command (lines 211-217) without any validation:

##### nltk/internals.py, lines 211-217 (HEAD)
if options is None:
    java_options = _java_options       # validated by config_java()
else:
    if isinstance(options, str):
        options = options.split()
    java_options = list(options)       # NO validation
cmd = [_java_bin] + java_options + cmd

Compare with config_java() (line 92) which does validate:

##### nltk/internals.py, lines 122-123
_validate_java_options(options)
_java_options[:] = options

The four affected wrapper classes store user-supplied java_options without validation and pass them through the unvalidated per-call path:

1. GenericStanfordParser (nltk/parse/stanford.py): constructor parameter at line 39, stored at line 78, passed at lines 247 and 256
2. StanfordTagger (nltk/tag/stanford.py): constructor parameter at line 51, stored at line 79, passed at line 118
3. StanfordTokenizer (nltk/tokenize/stanford.py): constructor parameter at line 43, stored at line 66, passed at line 109
4. StanfordSegmenter (nltk/tokenize/stanford_segmenter.py): constructor parameter at line 68, stored at line 117, passed at line 337

Proof of Concept

from nltk.internals import config_java, java, _validate_java_options

##### 1. The global config_java() path correctly blocks dangerous flags:
try:
    config_java(options=["-agentpath:/tmp/evil.so"])
except ValueError as e:
    print(f"config_java blocked: {e}")   # blocked as expected

##### 2. The per-call options path does NOT block them:

##### (Would execute if Java were installed)
##### java(["SomeClass"], classpath=".", options=["-agentpath:/tmp/evil.so"])

##### This passes "-agentpath:/tmp/evil.so" directly to subprocess.Popen

##### 3. Stanford wrapper classes pass through without validation:

##### from nltk.parse.stanford import StanfordParser
##### parser = StanfordParser(java_options="-agentpath:/tmp/evil.so")

##### parser.parse(...)  # dangerous flag reaches JVM

##### Verify the gap directly:
dangerous_opts = ["-agentpath:/tmp/evil.so"]
try:
    _validate_java_options(dangerous_opts)
    print("Would have been caught")
except ValueError:
    print("Correctly rejected by _validate_java_options()")

##### But java() itself never calls _validate_java_options():
import inspect
source = inspect.getsource(java)
assert "_validate_java_options" not in source, "java() does not validate options"
print("Confirmed: java() does not call _validate_java_options()")

Impact

An attacker who controls the java_options parameter to any NLTK Stanford wrapper class can inject arbitrary JVM flags, including:

• -agentpath:/path/to/malicious.so -- loads a native agent, achieving arbitrary code execution
• -javaagent:/path/to/malicious.jar -- loads a Java agent for bytecode manipulation
• -agentlib:jdwp=transport=dt_socket,server=y,address=*:5005 -- enables remote debugging, allowing remote code execution
• @/path/to/argfile -- expands an argument file, which can smuggle any of the above

This is exploitable in scenarios where NLTK is deployed as a service and java_options is derived from user input, configuration files, or environment variables. The PR #​3647 commit message explicitly states the fix was intended to cover "StanfordSegmenter, and GenericStanfordParser" but the implementation only validates in config_java().

Suggested Fix

Add _validate_java_options() to the java() function's per-call options handling:

##### nltk/internals.py, in the java() function
if options is None:
    java_options = _java_options
else:
    if isinstance(options, str):
        options = options.split()
    java_options = list(options)
    _validate_java_options(java_options)   # ADD THIS LINE
cmd = [_java_bin] + java_options + cmd

This single-line addition closes the bypass for all four Stanford wrapper classes and any future callers of java(options=...).

AI tooling

AI assistance was used for the code audit and for drafting this report. The finding were manually verified against the project's source at the location cited above before reporting it, and the severity and impact assessment are the reporters.

Severity

• CVSS Score: 9.3 / 10 (Critical)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

References

• https://github.com/nltk/nltk/security/advisories/GHSA-m4rf-3fr8-xwx3
• https://nvd.nist.gov/vuln/detail/CVE-2026-79675
• https://github.com/nltk/nltk/commit/8fa9650b6009aacfdebbc33d2a08d32c0858ea6c
• https://github.com/nltk/nltk/releases/tag/v3.10.3
• https://www.vulncheck.com/advisories/nltk-before-jvm-argument-injection-via-per-call-options
• https://github.com/advisories/GHSA-m4rf-3fr8-xwx3

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Release Notes

nltk/nltk (nltk)

v3.10.3

Compare Source

Version 3.10.3 2026-08-12

• docs: wrap Chat-80 HOWTO output
• Sandbox Stanford JAR execution to nltk_data directories
• Harden path-traversal / file-I/O sandbox: close write-side symlink TOCTOU + shared-temp squat, lock the cluster with a living audit (CWE-22/59/377)
• Extend algorithmic-complexity DoS hardening: repo-wide sweep + two-string distances (CWE-407/CWE-400)
• Bound unbounded-work DoS in parsers and grammar transforms (CWE-407/674/835)
• fix(security): sandbox MaltParser's Java execution (CVE-2026-12252, CVE-2026-12841)
• fix(security): trust the system temp dir only when it is private (CWE-377/CWE-378)
• fix(security): validate corpus-reader roots against the data sandbox (CWE-73)
• fix(security): validate per-call java() options and replace the -XX:/-D allowlist with a minimal one (CWE-88)
• Additional security hardening (CWE-407, CWE-426, CWE-427, CWE-502, CWE-59, CWE-776, CWE-918)

Thanks to the following contributors to 3.10.3: Mohammad Favas S, leduckhuong, Ziyu Lin, dougtrainer28-cmyk, Chaitanya Kadian, 0xRenSec, Arpit Jain, Jace, nguyencanhthuong, Liling Tan, medimedi, Eric Kafe.

What's Changed

• Sandbox Stanford JAR execution to nltk_data directories by @​ekaf in #​3743
• docs: wrap Chat-80 HOWTO output by @​medisean in #​3741
• ci: sandboxed-open guard + stabilize security tests across platforms/pythons (#​3740) by @​alvations in #​3744
• Prepare release 3.10.3 by @​ekaf in #​3745

New Contributors

• @​medisean made their first contribution in #​3741

Full Changelog: nltk/nltk@v3.10.2...v3.10.3

v3.10.2

Compare Source

Version 3.10.2 2026-08-05

• Remove inisec.py and document PYTHONSAFEPATH instead
• Skip draft step in release workflow
• Fix symlink escape in FramenetCorpusReader (CWE-59)
• Guard tempfile.gettempdir() when building pathsec allowed roots
• add tests for transitive_closure

Thanks to the following contributors to 3.10.2:
Litesh Ghute, Eric Kafe, Evan Kiefer, tarann26 and Rav Singh Chandan

v3.10.1

Compare Source

---

Configuration

📅 Schedule: (UTC)

• Branch creation
  • At any time (no schedule defined)
• Automerge
  • At any time (no schedule defined)

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

---

• If you want to rebase/retry this PR, check this box

---

This PR was generated by Mend Renovate. View the repository job log.

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.