TI-2026-55155 Aliases CVE-2026-79657 GHSA-x99w-6fgc-pmfw

NLTK before 3.10.3 Remote Code Execution via Unsafe Pickle Deserialization

HIGH 81CWE-502Published 2026-08-25 · Updated 2026-10-08

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Attack requirements: None
Impact type: Code execution, Security bypass
Confidentiality · integrity · availability: High · High · High
Fix status: Partial Red Hat: 1 fixed, 3 without a fix

Attack profile from CVSS 4.0 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-502 and CWE-693.

Summary

NLTK versions before 3.10.3 contain a remote code execution vulnerability in allowlisted pickle loaders that trust entire module namespaces instead of specific safe callables. Attackers can craft malicious pickle payloads invoking dangerous in-namespace functions like ReppTokenizer._execute and numpy.f2py.crackfortran.myeval through pickle REDUCE to execute arbitrary commands during model or tokenizer artifact loading.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV

EPSS 0.01267 69th percentileScored 2026-11-07

Public exploit Yes 1 exploit referenceTagged by NVD

Fix Partial nltk (nltk): 3.10.3nltk (PyPI): 3.10.3Red Hat: 1 advisoryRed Hat: 1 fixed, 3 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: Poc
Automatable: Yes
Technical impact: Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
nltk	nltk	before 3.10.3	3.10.3	Patch available	CNA
—	nltk (PyPI)	before 3.10.3	3.10.3	Patch available	GHSA-x99w-6fgc-pmfw

nltk Vendornltk Affected before 3.10.3 Fixed in 3.10.3 Patch available CNA
nltk (PyPI) Vendor— Affected before 3.10.3 Fixed in 3.10.3 Patch available GHSA-x99w-6fgc-pmfw

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:nltk:nltk::::::::	before 3.10.3	Vulnerable	nltk

cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:* Versions before 3.10.3 Vulnerable ·nltk

Remediation

Fix · CNA nltk (nltk) Fixed in 3.10.3
Fix · GHSA-x99w-6fgc-pmfw nltk (PyPI) Fixed in 3.10.3 Advisory →

Red Hat 1 advisory

RHSA-2026:84734 Released 2026-10-19 · Red Hat rating Critical
RHOAI 3.4.5 - Red Hat OpenShift AI
- Red Hat OpenShift AI 3.4 registry.redhat.io/rhoai/odh-ai-gateway-payload-processing-rhel9, registry.redhat.io/rhoai/odh-automl-rhel9, registry.redhat.io/rhoai/odh-autorag-rhel9 +47

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

Release · 2026-08-25
nltk 3.10.3
7 records Highest priority Priority HIGH 6 HIGH, 1 MEDIUM
Other records, highest priority first
- TI-2026-55173 NLTK before 3.10.3 JVM Argument Injection via Per-Call OptionsPriority HIGH 81
- TI-2026-55172 NLTK 3.10.2 Path Traversal via corpus-reader constructorsPriority HIGH 77
- TI-2026-54694 NLTK before 3.10.3 SSRF Protection Bypass via ProxyPriority HIGH 77
Show all 7 records →

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

Product	Status	Plan or fix
Lightspeed Core	Affected	No fix yet
OpenShift Lightspeed	Affected	No fix yet
Red Hat Ansible Automation Platform 2	Affected	No fix planned: Will not fix
Red Hat OpenShift AI 3.4	Fixed	RHSA-2026:84734

Not affected: 4 products

Lightspeed Core
OpenShift Lightspeed
Red Hat OpenShift AI (RHOAI)
Red Hat OpenShift AI 3.4

Timeline

2026-10-02 Threatist record created from CVE-2026-79657
2026-10-03 Alias added: GHSA-x99w-6fgc-pmfw
2026-10-20 Fix available: RHSA-2026:84734 · Red Hat
2026-10-20 Fix available: Red Hat OpenShift AI 3.4 · Red Hat

References

Exploit 1

GitHub Security Advisory (GHSA-x99w-6fgc-pmfw)

Advisory 1

https://nvd.nist.gov/vuln/detail/CVE-2026-79657

Other 4

TI-2026-00629 Arbitrary Code Execution in NLTK StanfordSegmenter via Untrusted JAR Loading CVSS 3.0CRITICAL 10.0
TI-2025-12800 Zip Slip Vulnerability in nltk/nltk Leading to Remote Code Execution CVSS 3.0CRITICAL 10.0
TI-2026-55173 NLTK before 3.10.3 JVM Argument Injection via Per-Call Options CVSS 4.0CRITICAL 9.3
TI-2026-56370 nltk PorterStemmer before 3.10.3 Quadratic-time DoS CVSS 4.0HIGH 8.7
TI-2026-55172 NLTK 3.10.2 Path Traversal via corpus-reader constructors CVSS 4.0HIGH 8.8
TI-2026-54694 NLTK before 3.10.3 SSRF Protection Bypass via Proxy CVSS 4.0HIGH 8.7

See all 41 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences