CVE-2026-126303
NLTK before 3.10.4 Denial of Service via SteppingRecursiveDescentParser.parse()
Description
NLTK before 3.10.4 contains an uncontrolled resource consumption vulnerability in SteppingRecursiveDescentParser.parse() that lacks any max_time deadline or step limit. Attackers influencing the grammar can supply an ambiguous self-embedding grammar and short token input to force unbounded top-down search, pinning CPU cores and exhausting worker pools.
INFO
Published Date :
Nov. 13, 2026, 9:36 a.m.
Last Modified :
Nov. 13, 2026, 9:36 a.m.
Remotely Exploit :
Yes !
Source :
VulnCheck
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | 83251b91-4cc7-4094-a5c7-464a1b83ea10 | ||||
| CVSS 3.1 | HIGH | MITRE-CVE | ||||
| CVSS 4.0 | HIGH | 83251b91-4cc7-4094-a5c7-464a1b83ea10 |
Solution
- Update NLTK to version 3.10.4 or later.
- Limit parser step counts.
- Configure parser time deadlines.
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CVE-2026-126303 vulnerability anywhere in the article.