CVE-2026-12243

✕ Withdrawn — historical dataHIGHPre-NVD 7.5
7.5CVSS

NLTK version 3.9.4 is vulnerable to a path traversal attack due to an incomplete fix for GitHub Issue #3504. The _UNSAFE_NO_PROTOCOL_RE regex in nltk/data.py checks for literal ../ sequences but fails to account for percent-encoded traversal sequences such as ..%2f. The url2pathname() function decodes these sequences after the validation step, allowing an attacker to bypass the protection. This vulnerability enables an attacker to read arbitrary files accessible to the Python process by controlling the resource name parameter passed to nltk.data.load() or nltk.data.find(). The issue affects applications that rely on NLTK for resource loading, including NLP web applications, Jupyter notebooks, and CLI tools. The default pathsec.ENFORCE=False setting exacerbates the impact by not blocking the file read at the open() stage.

CVSS v3
7.5
EchelonGraph score
Not yet assessedThis CVE record was withdrawn by its numbering authority, so there is no vulnerability to rate.
EPSS PROB
—
EPSS %ILE
—
KEV
—Not applicable: this CVE ID was withdrawn

Published

June 30, 2026

Last Modified

June 30, 2026

References (1)

Frequently asked(4)

What is CVE-2026-12243?
CVE-2026-12243 is a rejected CVE ID: its record was withdrawn on August 18, 2026 and no longer describes a vulnerability. Reason given: This CVE ID has been rejected or withdrawn by its CVE Numbering Authority.
When was the CVE record for CVE-2026-12243 published?
The CVE record for CVE-2026-12243 was published on June 30, 2026. EchelonGraph's copy of the record carries a last-modified date of June 30, 2026; the record at its source may have been updated since.
What is the CVSS score of CVE-2026-12243?
CVE-2026-12243 has a CVSS base score of 7.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-12243?
There is nothing to remediate under CVE-2026-12243: it is a rejected (withdrawn) CVE ID and no longer describes a vulnerability.