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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.5 · 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 · score source

EPSS

• CVE-2026-78680: 0.18% estimated exploitation activity in the next 30 days; percentile 7.27 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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 findbinary("dot") but discarded the returned validated path and then ran the bare name ["dot", ...], so the validation had no effect. - nltk.translate.api.AlignedSent.reprsvg — 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.findbinary 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…

Published by the source

1 Sep 2026, 20:27 UTC

Last modified by the source

1 Sep 2026, 20:27 UTC

Source last checked

26 Oct 2026, 13:51 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-6hwm-xvph-95vm

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# Patch Next advisory brief: CVE-2026-78680

Advisory: NLTK: Uncontrolled search path when invoking the Graphviz 'dot' binary
IDs: CVE-2026-78680, GHSA-6hwm-xvph-95vm
Record: https://patchnext.com/advisories/cve-2026-78680 (revision 1, source checked 26 Oct 2026, 13:51 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: nltk 3.10.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI nltk: affected <= 3.10.2; fixed in 3.10.3

## Suggested inspection (read-only)
- `python -m pip show nltk`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on nltk.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-6hwm-xvph-95vm (GitHub-reviewed advisory GHSA-6hwm-xvph-95vm lists affected ranges: PyPI nltk >=0 <=3.10.2)

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