{"id":"CVE-2026-128134","kind":"vulnerability","aliases":["CVE-2026-128134"],"related":[],"title":"NLTK: Graphviz path lookup lets local user run code as victim","description":"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.","summary":"NLTK's dependency graph renderer finds the Graphviz dot program through the PATH variable and runs it without its trusted-executable checks. A local user who can write to a PATH directory on a POSIX system can plant a fake dot program that runs as the victim when dot2img or DependencyGraph.repr_svg is called.","severity":"high","cvss":7.8,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["graphviz","nltk","package","posix","python"],"not_affected_if":["nltk-3.10.4-or-later","no-graphviz-rendering","no-untrusted-local-users"],"how_to_check":"- Check the installed NLTK version with `python -c \"import nltk; print(nltk.__version__)\"`, and treat any version below `3.10.4` as affected.\n- Look for writable directories on the PATH of hosts that run NLTK, for example with `echo $PATH` and `ls -ld` on each entry.","fix":"- NLTK: upgrade to `3.10.4`.","status":"open","published_at":"2026-11-13T23:17:17+00:00","first_seen_at":"2026-11-13T23:35:10+00:00","triaged_at":"2026-11-13T23:37:00+00:00","updated_at":"2026-11-13T23:37:00+00:00","category":"package","confidence":0.8,"triage":{"at":"2026-11-13T23:37:00Z","model":"claude-haiku-5-5","output":{"fix":"- NLTK: upgrade to `3.10.4`.","reach":"local","title":"NLTK: Graphviz path lookup lets local user run code as victim","impact":"high","summary":"NLTK's dependency graph renderer finds the Graphviz dot program through the PATH variable and runs it without its trusted-executable checks. A local user who can write to a PATH directory on a POSIX system can plant a fake dot program that runs as the victim when dot2img or DependencyGraph.repr_svg is called.","audience":"developers","category":"package","nicknames":[],"who_cares":["python","nltk","posix","graphviz"],"confidence":0.8,"fix_status":"available","needs_auth":"yes","worst_case":"Local attacker runs code as the victim user","analyst_note":"","how_to_check":"- Check the installed NLTK version with `python -c \"import nltk; print(nltk.__version__)\"`, and treat any version below `3.10.4` as affected.\n- Look for writable directories on the PATH of hosts that run NLTK, for example with `echo $PATH` and `ls -ld` on each entry.","plain_action":"","product_name":"","needs_analyst":false,"not_affected_if":["nltk-3.10.4-or-later","no-graphviz-rendering","no-untrusted-local-users"],"who_is_affected":"Only POSIX systems where NLTK's dependency graph code (dot2img or DependencyGraph.repr_svg) runs and where a low-privileged local user can write to a PATH directory. The sources say the current-directory bare-name case is a separate, already blocked issue. Environments with no writable PATH entries and no local untrusted users are lower risk.","user_interaction":"no","product_ecosystem":"","needs_special_setup":"yes","severity_if_unknown":"unknown"},"cost_usd":0.000784,"input_tokens":4807,"output_tokens":607,"severity_before":"high"},"analyst_status":null,"analyst_note":null,"search":"'-128134':14A,17A '-2026':13A,16A,211C '-78680':212C '3.10.4':104C,219C 'absolut':118C,205C 'attack':147C 'bare':189C 'bare-nam':188C 'block':193C 'bypass':208C 'call':77B,174C 'check':45B 'code':9A,166C 'current':184C 'current-working-directory-on':183C 'cve':12A,15A,210C 'data':90C 'depend':25B 'dependencygraph.repr':74B,177C 'develop':97C 'direct':175C 'directori':55B,153C,186C 'dot':31B,64B,110C,164C 'dot2img':72B,106C,172C 'element':207C 'env':135C 'environ':137C 'execut':44B,111C,119C,128C,167C 'fake':63B 'find':28B 'fix':216C 'graph':26B,181C 'graphviz':2A,18B,30B,109C 'invok':115C 'issu':200C,214C 'languag':80C,100C 'let':5A 'loader':136C 'local':6A,47B,143C 'lookup':4A 'low':145C 'low-privileg':144C 'modul':89C 'name':190C 'natur':79C,99C 'nltk':1A,19B,23B,78C 'nltk.parse.dependencygraph':105C 'open':86C 'ownership':129C 'packag':20B 'path':3A,35B,54B,113C,159C,206C 'plant':61B,161C 'posix':21B,58B,156C 'prior':102C 'privileg':146C 'process':101C 'program':32B,65B 'python':22B,88C 'render':27B,179C 'replac':163C 'research':95C 'residu':203C 'resolv':107C,126C 'result':117C 'rout':121C 'run':8A,38B,67B,141C 'safe':134C 'scrub':138C 'set':91C 'sourc':87C 'spawn':123C 'suit':84C 'support':94C 'svg':75B,178C 'system':59B 'toolkit':81C 'trust':43B,124C,127C 'trusted-execut':42B 'tutori':93C 'user':7A,48B 'valid':132C 'variabl':36B 'vector':191C 'version':218C 'victim':11A,70B,157C,170C 'vulner':198C 'without':40B,120C 'work':185C 'writabl':131C,204C 'write':51B,150C","nicknames":[],"mitigations":[],"who_affected":"Only POSIX systems where NLTK's dependency graph code (dot2img or DependencyGraph.repr_svg) runs and where a low-privileged local user can write to a PATH directory. The sources say the current-directory bare-name case is a separate, already blocked issue. Environments with no writable PATH entries and no local untrusted users are lower risk.","tier":"B","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"developers","plain_action":null,"pkeys":[],"ptokens":[],"labels":["graphviz","high","nltk","package","posix","python"],"campaign_type":null,"search_a":"'-128134':14A,17A '-2026':13A,16A 'code':9A 'cve':12A,15A 'graphviz':2A 'let':5A 'local':6A 'lookup':4A 'nltk':1A 'path':3A 'run':8A 'user':7A 'victim':11A","search_b":"'call':77B 'check':45B 'depend':25B 'dependencygraph.repr':74B 'directori':55B 'dot':31B,64B 'dot2img':72B 'execut':44B 'fake':63B 'find':28B 'graph':26B 'graphviz':18B,30B 'local':47B 'nltk':19B,23B 'packag':20B 'path':35B,54B 'plant':61B 'posix':21B,58B 'program':32B,65B 'python':22B 'render':27B 'run':38B,67B 'svg':75B 'system':59B 'trust':43B 'trusted-execut':42B 'user':48B 'variabl':36B 'victim':70B 'without':40B 'write':51B","search_c":"'-2026':211C '-78680':212C '3.10.4':104C,219C 'absolut':118C,205C 'attack':147C 'bare':189C 'bare-nam':188C 'block':193C 'bypass':208C 'call':174C 'code':166C 'current':184C 'current-working-directory-on':183C 'cve':210C 'data':90C 'dependencygraph.repr':177C 'develop':97C 'direct':175C 'directori':153C,186C 'dot':110C,164C 'dot2img':106C,172C 'element':207C 'env':135C 'environ':137C 'execut':111C,119C,128C,167C 'fix':216C 'graph':181C 'graphviz':109C 'invok':115C 'issu':200C,214C 'languag':80C,100C 'loader':136C 'local':143C 'low':145C 'low-privileg':144C 'modul':89C 'name':190C 'natur':79C,99C 'nltk':78C 'nltk.parse.dependencygraph':105C 'open':86C 'ownership':129C 'path':113C,159C,206C 'plant':161C 'posix':156C 'prior':102C 'privileg':146C 'process':101C 'python':88C 'render':179C 'replac':163C 'research':95C 'residu':203C 'resolv':107C,126C 'result':117C 'rout':121C 'run':141C 'safe':134C 'scrub':138C 'set':91C 'sourc':87C 'spawn':123C 'suit':84C 'support':94C 'svg':178C 'toolkit':81C 'trust':124C,127C 'tutori':93C 'valid':132C 'vector':191C 'version':218C 'victim':157C,170C 'vulner':198C 'without':120C 'work':185C 'writabl':131C,204C 'write':150C","cause_entry":null,"cause_path":null,"disclosures_checked_at":null,"first_public_at":"2026-10-26T09:57:03+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cvss_by":"security-advisories@github.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-128134","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-128134","severity":null,"published_at":"2026-11-13T23:17:17+00:00","modified_at":"2026-11-13T23:17:18+00:00","first_seen_at":"2026-11-13T23:35:10+00:00","fetched_at":"2026-11-13T23:35:10+00:00","note":null}],"documents":[{"id":151008,"url":"https://github.com/nltk/nltk/commit/b002a7288c22db86fd6ca2d9526e3f91d6fda797","title":"Patch: github.com","kind":"other","source":"nvd","publisher":"vendor","text":null,"published_at":null,"relation":"fix","confidence":null,"note":"Patch: github.com"},{"id":149657,"url":"https://github.com/nltk/nltk/releases/tag/v3.10.4","title":"Release: github.com","kind":"release","source":"ghsa","publisher":"vendor","text":null,"published_at":null,"relation":"fix","confidence":null,"note":"Release notes: github.com"},{"id":151010,"url":"https://github.com/nltk/nltk/security/advisories/GHSA-7mxv-7h3q-9324","title":"Vendor advisory: github.com","kind":"vendor","source":"nvd","publisher":"vendor","text":null,"published_at":"2026-10-26T09:57:03+00:00","relation":"advisory","confidence":null,"note":"Vendor advisory: github.com"}],"disclosures":[],"exploit_sources":[],"notice":"Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai"}