CVE•Published 2026-08-26•Modified 2026-09-01•0 articles on news•5 live references•NVD data

CVE-2026-80206Nltk · Nltk

Vulnerability data via NVD (ingested)

CVSS v3.1

5.9

MEDIUM

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

EPSS percentile

Exploit Prediction Scoring System · top 84% of all CVEs

Weaknesses (CWE)

CWE-1333Inefficient Regular Expression Complexity

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.

Timeline

Published 2026-08-26

Modified 2026-09-01

External references

NVD MITRE Exploit-DB trickest/cve VulnCheck

Search for exposed instances

Shodan + Censys queries derived from NVD's CPE data. The vuln tag catches assets Shodan has explicitly linked to this CVE; the product / banner fingerprints find exposed instances even when the vuln tag was never applied (which is common).

Shodan · vuln tag0 hosts

vuln:CVE-2026-80206

Hosts Shodan has explicitly fingerprinted as vulnerable.

Shodan · product

product:"Nltk Nltk"

All exposed Nltk Nltk instances — cross-reference with the CVE's affected-version range.

Shodan · banner/body mention

http.html:"Nltk"

HTTP body or banner mentions "Nltk" — catches deploys Shodan didn't identify as a product.

More intel sources (5)

Shodan report

vuln:CVE-2026-80206