CVE-2026-71513: NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only th

Q: How do I fix CVE-2026-71513?

nltk: upgrade to 3.10.3. Exact commands for each OS are on this page.

Q: Is CVE-2026-71513 being exploited?

CVE-2026-71513 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-71513 affect?

CVE-2026-71513 affects nltk. Severity is high (CVSS 8.8). NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only the pickle module string and not the global name, allowing attackers to resolve dotted names by attribute traversal to callables out

This month

HIGH 8.8UPGRADE

CVE-2026-71513 is a high-severity flaw (CVSS 8.8) affecting nltk. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only the pickle module string and not the global name, allowing attackers to resolve dotted names by attribute traversal to callables outside the allowlisted namespace. Attackers can craft untrusted transition-parser models that execute arbitrary commands when TransitionParser.parse loads the model through allowlisted_pickle_load.

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	1.1% (top 35%)
CISA exploited list	No
Weakness	CWE-502
Published	2026-08-22
Last modified	2026-10-14

Publisher (CNA): VulnCheck · Vendor: nltk

Last updated 2026-10-14 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-08-22 14:16 UTCPublished CVE record published
2026-10-14 19:10 UTCUpdated Record last modified

nltk nltk UPGRADE

Affected: < 3.10.3

Fixed in: 3.10.3

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy nltk || rpm -q nltk || nltk --version

2. UPGRADE to 3.10.3 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade nltk

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade nltk

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-71513?

nltk: upgrade to 3.10.3. Exact commands for each OS are on this page.

Is CVE-2026-71513 being exploited?

CVE-2026-71513 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-71513 affect?

CVE-2026-71513 affects nltk. Severity is high (CVSS 8.8). NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only the pickle module string and not the global name, allowing attackers to resolve dotted names by attribute traversal to callables out

How urgent is CVE-2026-71513?

Priority 47/100. High severity

Related CVEs

CVE-2026-12252 HIGH 7.8 UPGRADE In nltk/nltk versions 3.9.3 and earlier, five Stanford interface classes (StanfordPOSTagger, StanfordNERTagger
CVE-2026-12259 MEDIUM 6.5 DOWNGRADE In nltk version 3.9.4, the `nltk.downloader.Downloader._download_package()` function writes downloaded package
CVE-2026-12261 MEDIUM 6.5 UPGRADE A vulnerability in `nltk.downloader` in nltk/nltk versions <= 3.9.4 allows for cross-package resource and mode
CVE-2026-12372 LOW 3.7 DOWNGRADE A Server-Side Request Forgery (SSRF) vulnerability exists in nltk/nltk versions 3.9.4 and the current develop
CVE-2026-71514 LOW 2.5 UPGRADE NLTK 3.9.4 through 3.10.2 contains a path traversal vulnerability in CrubadanCorpusReader

References

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