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

• PyPI nltk: < 3.10.3 → fixed in 3.10.3

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 ( 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.