# CVE-2026-128134: NLTK dot2img runs Graphviz 'dot' without the trusted-exec chokepoint, enabling local code execution via a writable PATH element

Status: published. Published: 2026-11-13. Updated: 2026-11-13.

NLTK (Natural Language Toolkit) is a suite of open source Python modules, data sets, and tutorials supporting research and development in Natural Language Processing. Prior to 3.10.4, nltk.parse.dependencygraph.dot2img resolves the Graphviz dot executable through PATH but invokes the resulting absolute executable without routing through spawn_trusted, so resolve_trusted_executable ownership and writability validation and safe_env loader environment scrubbing do not run. A local low-privileged attacker who can write to a directory on a POSIX victim's PATH can plant or replace dot, and code executes as the victim when dot2img is called directly or DependencyGraph.repr_svg renders a graph. The current-working-directory-only bare-name vector is blocked and is not this vulnerability; this issue is the residual writable absolute PATH element bypass after CVE-2026-78680. This issue is fixed in version 3.10.4.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- nltk / nltk: < 3.10.4 (affected). Source: CNA: GitHub_M

## Severity and prioritization

- CVSS 3.1: 7.8 (high); CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H; source: CNA: GitHub_M

- CVSS 3.1: 7.8 (high); CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H; source: NVD: security-advisories@github.com

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-426, CWE-427

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/nltk/nltk/security/advisories/GHSA-7mxv-7h3q-9324 (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/nltk/nltk/pull/3887 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/nltk/nltk/commit/b002a7288c22db86fd6ca2d9526e3f91d6fda797 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/nltk/nltk/releases/tag/v3.10.4 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/nltk/nltk/commit/b002a7288c22db86fd6ca2d9526e3f91d6fda797 (security-advisories@github.com)

- https://github.com/nltk/nltk/pull/3887 (security-advisories@github.com)

- https://github.com/nltk/nltk/releases/tag/v3.10.4 (security-advisories@github.com)

- https://github.com/nltk/nltk/security/advisories/GHSA-7mxv-7h3q-9324 (security-advisories@github.com)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-128134; retrieved 2026-11-13; source updated 2026-11-13

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-128134; retrieved 2026-11-14; source updated 2026-11-13

Revision: 2b1e20fb1a515c01c56e626992a815a268ac38db62b02905df71ab24591314b1

Canonical: https://y2.dev/cve/CVE-2026-128134

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.