CVE-2026-81726 NLTK through 3.10.3 Path Traversal via Model-Artifact APIs

What is CVE-2026-81726?

CVE-2026-81726 is a high-severity path traversal vulnerability in nltk, published on 27 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

NLTK through 3.10.3 contains a path traversal vulnerability in model-artifact APIs that bypass pathsec enforcement by using raw file operations on caller-controlled paths. Attackers can read or write files outside allowed sandbox roots through TransitionParser, AveragedPerceptron, PerceptronTagger, and maxent parameter APIs when pathsec is enabled.

Weakness: CWE-73

Which versions are affected by CVE-2026-81726?

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

Products include Nltk Nltk.

How do I fix CVE-2026-81726?

Upgrade nltk to 3.10.3 or later.

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

Is CVE-2026-81726 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-81726 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-2026-81726, GHSA-8mgp-746c-j5xp, PYSEC-2026-3740, UBUNTU-CVE-2026-81726, openSUSE-SU-2026:12280-1.