CVE-2026-70626 NLTK before 3.9.4 Symlink Escape via CorpusReader

What is CVE-2026-70626?

CVE-2026-70626 is a high-severity path traversal vulnerability in nltk, published on 22 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

NLTK versions before 3.9.4 contain a symlink escape vulnerability in CorpusReader.open() that allows local attackers to read arbitrary files outside the corpus root. The vulnerability exists because path validation is lexical and does not account for symlink resolution, enabling attackers to place symlinks inside the corpus root to access files outside the intended boundary.

Weakness: CWE-59

Which versions are affected by CVE-2026-70626?

3 open source packages ship an affected version, including nltk. It affects 1 product.

Products include Nltk Nltk.

How do I fix CVE-2026-70626?

Upgrade nltk to 3.9.4 or later.

Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.

Is CVE-2026-70626 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-70626 exists.

Other vulnerabilities in nltk

• CVE-2026-0848 Arbitrary Code Execution in NLTK StanfordSegmenter via Untrusted JAR Loading Critical 10.0
• CVE-2025-14009 Zip Slip Vulnerability in nltk/nltk Leading to Remote Code Execution Critical 10.0
• CVE-2026-78683 NLTK before 3.10.0 Remote Code Execution via Unsafe Pickle Deserialization Critical 9.4
• CVE-2026-79657 NLTK before 3.10.3 Remote Code Execution via Unsafe Pickle Deserialization Critical 9.3
• CVE-2026-79675 NLTK before 3.10.3 JVM Argument Injection via Per-Call Options Critical 9.3

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2026-70626, ECHO-9e81-b61d-422b, GHSA-r6gq-whwq-mvg9, MINI-7qrv-vmhw-6pwf, PYSEC-2026-3732, UBUNTU-CVE-2026-70626.