Bug 2573542 (CVE-2026-128134)

Summary:	CVE-2026-128134 nltk: nltk: Arbitrary code execution via untrusted search path
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	unspecified	CC:	anpicker, ebourniv, hasun, jfula, jlanda, jowilson, kshier, nyancey, ometelka, ptisnovs, rbobbitt, sbunciak, simaishi, stcannon, syedriko, xdharmai, yguenane
Target Milestone:	---	Keywords:	Security
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Hardware:	All
OS:	Linux
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Doc Text:	A flaw was found in NLTK. When rendering dependency graphs, the library resolves the external Graphviz executable through the system execution search path (PATH) without verifying directory ownership or write permissions. A local attacker with write access to a directory listed on a user's PATH can place a malicious executable to be invoked during graph visualization. This issue allows the attacker to achieve arbitrary code execution with the permissions of the user running the application.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-11-13 22:31:36 UTC

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.