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BREW-acronym-CVE-2026-78680 — NLTK: Uncontrolled search path when invoking the Graphviz 'dot' binary

Affected: Homebrew: acronym

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.

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## 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...…

CVE-2026-78680 — NLTK before 3.10.3 Arbitrary Code Execution via Graphviz dot Binary

Affected: nltk

NLTK versions before 3.10.3 fail to use validated absolute paths when invoking the Graphviz dot binary in dependencygraph.dot2img and AlignedSent._repr_svg_, allowing attackers to execute arbitrary code by placing a malicious dot binary in the search path or current working directory. Attackers can exploit bare-name binary resolution on Windows via the current working directory or on Unix-like systems via relative PATH entries to execute their binary instead of the legitimate Graphviz tool.

GHSA-6hwm-xvph-95vm — NLTK: Uncontrolled search path when invoking the Graphviz 'dot' binary

Affected: PyPI: nltk

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## 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...…