Vulnerability-Lookup

GHSA-VF76-F5CP-9846

Vulnerability from github – Published: 2026-08-31 21:31 – Updated: 2026-09-02 14:49

Withdrawn 2026-09-02

Summary

Duplicate Advisory: ReDoS in nltk.tgrep via unvalidated user-supplied regular expressions

Details

Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-w3v8-gmh9-3wv7. This link is maintained to preserve external references.

Original Description

NLTK before 3.10.3 contains a regular expression denial of service (ReDoS) vulnerability in the tgrep module. The _tgrep_node_action function compiles user-supplied regular expressions embedded in /regex/ pattern nodes and executes them via re.search against tree node labels without any validation or timeout. An attacker who controls the tgrep pattern (e.g., via tgrep_positions() or tgrep_compile() exposed to external input) can supply a pattern that triggers catastrophic backtracking, causing indefinite CPU saturation that blocks the Python process.

Severity

5.9 (Medium)


                  
                    CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

8.2 (High)


                  
                    CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

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JSON

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{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "nltk"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "3.10.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-1333"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-02T14:49:37Z",
    "nvd_published_at": "2026-08-26T11:16:40Z",
    "severity": "HIGH"
  },
  "details": "## Duplicate Advisory\n\nThis advisory has been withdrawn because it is a duplicate of\u00a0GHSA-w3v8-gmh9-3wv7. This link is maintained to preserve external references.\n\n## Original Description\nNLTK before 3.10.3 contains a regular expression denial of service (ReDoS) vulnerability in the tgrep module. The _tgrep_node_action function compiles user-supplied regular expressions embedded in /regex/ pattern nodes and executes them via re.search against tree node labels without any validation or timeout. An attacker who controls the tgrep pattern (e.g., via tgrep_positions() or tgrep_compile() exposed to external input) can supply a pattern that triggers catastrophic backtracking, causing indefinite CPU saturation that blocks the Python process.",
  "id": "GHSA-vf76-f5cp-9846",
  "modified": "2026-09-02T14:49:37Z",
  "published": "2026-08-31T21:31:52Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/nltk/nltk/security/advisories/GHSA-w3v8-gmh9-3wv7"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-80206"
    },
    {
      "type": "WEB",
      "url": "https://www.vulncheck.com/advisories/nltk-3.10.2-regular-expression-denial-of-service-via-tgrep"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Duplicate Advisory: ReDoS in nltk.tgrep via unvalidated user-supplied regular expressions",
  "withdrawn": "2026-09-02T14:49:37Z"
}

CVE-2026-80206 (GCVE-0-2026-80206)

Vulnerability from cvelistv5 – Published: 2026-08-26 10:28 – Updated: 2026-08-26 12:52

Title

NLTK 3.10.2 Regular Expression Denial of Service via tgrep

Summary

Severity

8.2 (High)


                        
                          CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

5.9 (Medium)


                        
                          CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-26 12:52 UTC

CWE

CWE-1333 - Inefficient Regular Expression Complexity

Assigner

VulnCheck mitre root

References

2 references

URL	Tags
https://github.com/nltk/nltk/security/advisories/…	vendor-advisory
https://www.vulncheck.com/advisories/nltk-3.10.2-…	third-party-advisory

Impacted products

1 product

Vendor	Product	Version
nltk	nltk	Affected: 0 , < 3.10.3 (semver) Unaffected: 3.10.3 (semver) cpe:2.3:a:nltk:nltk::::::::

Date Public

2026-08-12 00:00

Credits

infycore ekaf agent-kira

Show details on NVD website

JSON

To clipboard

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  "containers": {
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      {
        "metrics": [
          {
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                "id": "CVE-2026-80206",
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                  },
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                    "Technical Impact": "partial"
                  }
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                "role": "CISA Coordinator",
                "timestamp": "2026-08-26T12:52:03.078501Z",
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}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.