CVE-2026-63311

creationtimestamp| type| source ---|---|--- 2026-09-02 16:35:05+00:00| published-proof-of-concept| https://github.com/nltk/nltk/security/advisories/GHSA-3gqm-fcw5-w839 2026-09-02 21:32:05+00:00| seen| https://gist.github.com/alon710/d2b8511d121d9c8c1d87b14251d4a3da...

EUVD-2026-64336

NLTK: Default ENFORCE=False Disables All pathsec Security Controls...

NLTK: Default ENFORCE=False Disables All pathsec Security Controls

NLTK's pathsec.py security module defaults to ENFORCE=False line 24, which means all 8 security validation functions only emit RuntimeWarning instead of raising exceptions when violations are detected. The pathsec module was introduced as the fix for CVE-2024-39705 arbitrary code execution via...

GHSA-P3M8-78J2-G5P3 NLTK: Default ENFORCE=False Disables All pathsec Security Controls

NLTK's pathsec.py security module defaults to ENFORCE=False line 24, which means all 8 security validation functions only emit RuntimeWarning instead of raising exceptions when violations are detected. The pathsec module was introduced as the fix for CVE-2024-39705 arbitrary code execution via...

NLTK: SSRF Fail-Open in validate_network_url() via DNS Resolution Failure

There is an SSRF vulnerability in NLTK 3.9.4's network URL validation. The validatenetworkurl function in nltk/pathsec.py fails open when DNS resolution returns an error. The resolvehostname helper at lines 193-234 catches OSError and ValueError during socket.getaddrinfo and returns an empty list...

GHSA-3GQM-FCW5-W839 NLTK: SSRF Fail-Open in validate_network_url() via DNS Resolution Failure

There is an SSRF vulnerability in NLTK 3.9.4's network URL validation. The validatenetworkurl function in nltk/pathsec.py fails open when DNS resolution returns an error. The resolvehostname helper at lines 193-234 catches OSError and ValueError during socket.getaddrinfo and returns an empty list...

EUVD-2026-64334

NLTK: SSRF Fail-Open in validatenetworkurl via DNS Resolution Failure...

GHSA-WW6M-CW3F-Q94G NLTK: Quadratic-time DoS in PorterStemmer via long runs of 'y'

nltk.stem.PorterStemmer.stem -- a ubiquitous public API applied to arbitrary, often untrusted, tokens -- runs in On^2 time on a token containing a long run of the letter 'y', letting a single 20-50 KB token pin a CPU core CWE-407. Root cause isconsonantword, i was made iterative commit for 3633,...

EUVD-2026-67072

NLTK: Quadratic-time DoS in PorterStemmer via long runs of 'y'...

NLTK: Quadratic-time DoS in PorterStemmer via long runs of 'y'

nltk.stem.PorterStemmer.stem -- a ubiquitous public API applied to arbitrary, often untrusted, tokens -- runs in On^2 time on a token containing a long run of the letter 'y', letting a single 20-50 KB token pin a CPU core CWE-407. Root cause isconsonantword, i was made iterative commit for 3633,...

NLTK: Downloader.download follows hardlinks and overwrites outside-root files

Summary NLTK's downloader now blocks symlink escapes during ZIP extraction, but it still treats pre-existing hardlinks inside the install tree as ordinary in-root files. A normal package install can therefore overwrite an outside-root inode through that hardlink. Details - Vulnerability type:...

EUVD-2026-67077

NLTK: Downloader.download follows hardlinks and overwrites outside-root files...

GHSA-F794-5JV7-7672 NLTK: Downloader.download follows hardlinks and overwrites outside-root files

Summary NLTK's downloader now blocks symlink escapes during ZIP extraction, but it still treats pre-existing hardlinks inside the install tree as ordinary in-root files. A normal package install can therefore overwrite an outside-root inode through that hardlink. Details - Vulnerability type:...

External Control of File Name or Path

Overview nltk is a Natural Language Toolkit NLTK is a Python package for natural language processing. Affected versions of this package are vulnerable to External Control of File Name or Path via the Downloader.download and Downloader.incrdownload file-write path in nltk/downloader.py. An attacke...

EUVD-2026-67076

NLTK: Model-artifact APIs bypass pathsec and touch files outside allowed roots...

NLTK: Model-artifact APIs bypass pathsec and touch files outside allowed roots

Summary Several model-artifact APIs still treat caller-controlled model paths as ordinary filenames even when NLTK path security is enforced. The same outside-root paths are rejected by guarded helpers, but these public read and write flows still use raw file APIs. Details - Vulnerability type:...

GHSA-8MGP-746C-J5XP NLTK: Model-artifact APIs bypass pathsec and touch files outside allowed roots

Summary Several model-artifact APIs still treat caller-controlled model paths as ordinary filenames even when NLTK path security is enforced. The same outside-root paths are rejected by guarded helpers, but these public read and write flows still use raw file APIs. Details - Vulnerability type:...

NLTK: Quadratic CPU Exhaustion in `XMLCorpusView._read_xml_fragment()`

Summary XMLCorpusView.readxmlfragment reads a corpus file in 1 KiB blocks, appending each block to a growing fragment string, then calls VALIDXMLRE.matchfragment on the full accumulated buffer every iteration. Because each iteration rescans the entire accumulated fragment, the total amount of wor...

EUVD-2026-67073

NLTK: Quadratic CPU Exhaustion in XMLCorpusView.readxmlfragment...

GHSA-VP2X-QP44-57V7 NLTK: Quadratic CPU Exhaustion in `XMLCorpusView._read_xml_fragment()`

Summary XMLCorpusView.readxmlfragment reads a corpus file in 1 KiB blocks, appending each block to a growing fragment string, then calls VALIDXMLRE.matchfragment on the full accumulated buffer every iteration. Because each iteration rescans the entire accumulated fragment, the total amount of wor...