NLTK before 3.10.0 ReDoS via Text.findall() unvalidated regex
Priority MEDIUM 45CWE-1333Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Partial Red Hat: 4 fixed, 5 without a fix
Attack profile from CVSS 4.0 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-1333.
Summary
NLTK versions before 3.10.0 contain a regular expression denial of service vulnerability in Text.findall() and TokenSearcher.findall() methods that accept user-supplied regular expressions without validation or timeout. Attackers can supply crafted regex patterns that cause catastrophic backtracking, resulting in indefinite CPU saturation and denial of service to all users of the Python process.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00651 51st percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Partial nltk (nltk): 3.10.0nltk (PyPI): 3.10.0Red Hat: 5 advisoriesRed Hat: 4 fixed, 5 without a fix
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
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 3.10.0 | 3.10.0 | Patch available | CNA |
| — | nltk (PyPI) | before 3.10.0 | 3.10.0 | Patch available | GHSA-rrv8-h7p8-rx55 |
- nltk Vendornltk Affected before 3.10.0 Fixed in 3.10.0 Patch available CNA
- nltk (PyPI) Vendor— Affected before 3.10.0 Fixed in 3.10.0 Patch available GHSA-rrv8-h7p8-rx55
Remediation
- Fix · CNA nltk (nltk) Fixed in 3.10.0
- Fix · GHSA-rrv8-h7p8-rx55 nltk (PyPI) Fixed in 3.10.0 Advisory →
Red Hat 5 advisories
- RHSA-2026:87410 Released 2026-10-21 · Red Hat rating CriticalRHOAI 2.25.12 - Red Hat OpenShift AI
- Red Hat OpenShift AI 2.25 registry.redhat.io/rhoai/odh-built-in-detector-rhel9, registry.redhat.io/rhoai/odh-caikit-nlp-rhel9, registry.redhat.io/rhoai/odh-codeflare-operator-rhel9 +47
- RHSA-2026:86891 Released 2026-10-21 · Red Hat rating CriticalRHOAI 3.5.2 - Red Hat OpenShift AI
- Red Hat OpenShift AI 3.5 registry.redhat.io/rhoai/odh-automl-rhel9, registry.redhat.io/rhoai/odh-built-in-detector-rhel9, registry.redhat.io/rhoai/odh-cli-rhel9 +47
- RHSA-2026:84734 Released 2026-10-19 · Red Hat rating CriticalRHOAI 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
Show 2 more Red Hat advisories
- RHSA-2026:73987 Released 2026-09-30 · Red Hat rating CriticalRHOAI 3.3.7 - Red Hat OpenShift AI
- Red Hat OpenShift AI 3.3 registry.redhat.io/rhoai/odh-built-in-detector-rhel9, registry.redhat.io/rhoai/odh-dashboard-rhel9, registry.redhat.io/rhoai/odh-data-science-pipelines-argo-argoexec-rhel9 +47
- RHSA-2026:69539 Released 2026-09-21 · Red Hat rating ImportantRHOAI 3.5.1 - Red Hat OpenShift AI
- Red Hat OpenShift AI 3.5 registry.redhat.io/rhoai/odh-cli-rhel9, registry.redhat.io/rhoai/odh-mlserver-cuda-rhel9, registry.redhat.io/rhoai/odh-mlserver-rhel9 +28
Vendor assessments
Red Hat
Red Hat rating: Important. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Exploit Intelligence | Affected | No fix planned: Will not 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 (RHOAI) | Affected | No fix yet |
| Red Hat OpenShift AI 2.25 | Fixed | RHSA-2026:87410 |
| Red Hat OpenShift AI 3.3 | Fixed | RHSA-2026:73987 |
| Red Hat OpenShift AI 3.4 | Fixed | RHSA-2026:84734 |
| Red Hat OpenShift AI 3.5 | Fixed | RHSA-2026:69539, RHSA-2026:86891 |
Not affected: 5 products
- OpenShift Lightspeed
- Red Hat OpenShift AI 2.25
- Red Hat OpenShift AI 3.3
- Red Hat OpenShift AI 3.4
- Red Hat OpenShift AI 3.5
Timeline
- 2026-10-02 Threatist record created from CVE-2026-80205
- 2026-10-03 Alias added: GHSA-rrv8-h7p8-rx55
- 2026-10-07 Fix available: RHSA-2026:73987 · Red Hat
- 2026-10-14 EPSS moved to the 50th–90th percentile
- 2026-10-20 Fix available: RHSA-2026:84734 · Red Hat
- 2026-10-20 Fix available: Red Hat OpenShift AI 3.4 · Red Hat
- 2026-10-22 Fix available: RHSA-2026:86891 · Red Hat
- 2026-10-22 Fix available: RHSA-2026:87410 · Red Hat
- 2026-10-23 Fix available: Red Hat OpenShift AI 2.25 · Red Hat
References
Other 6
- https://github.com/nltk/nltk/pull/3674
- https://github.com/nltk/nltk/commit/d8e47539317b571ab1422981f5b9653d5eae1249
- https://github.com/nltk/nltk
- https://github.com/nltk/nltk/releases/tag/v3.10.0
- https://github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-3750.yaml
- http://www.openwall.com/lists/oss-security/2026/09/01/3
More Nltk vulnerabilities
- 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-2026-55155 NLTK before 3.10.3 Remote Code Execution via Unsafe Pickle Deserialization 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
Sources
- CVE-2026-80205 · CVE Program
- CVE-2026-80205 · NVD
- FIRST EPSS
- GHSA-rrv8-h7p8-rx55 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-80205 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences