CVE-2026-80206
NLTK 3.10.2 Regular Expression Denial of Service via tgrep
CVSS Score
5.9
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-1333 |
| Vendor | nltk |
| Product | nltk |
| Published | Aug 26, 2026 |
| Last Updated | Aug 26, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Affected Versions
nltk / nltk
0 < 3.10.3
References
Credits
🔍 infycore ekaf agent-kira