CVE-2026-80206
NLTK 3.10.2 Regular Expression Denial of Service via tgrep
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.
INFO
Published Date :
Aug. 26, 2026, 10:28 a.m.
Last Modified :
Aug. 26, 2026, 10:28 a.m.
Remotely Exploit :
Yes !
Source :
VulnCheck
Affected Products
The following products are affected by CVE-2026-80206
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | 83251b91-4cc7-4094-a5c7-464a1b83ea10 | ||||
| CVSS 3.1 | MEDIUM | MITRE-CVE | ||||
| CVSS 4.0 | HIGH | 83251b91-4cc7-4094-a5c7-464a1b83ea10 |
Solution
- Update NLTK to version 3.10.3 or later.
- Avoid processing untrusted regular expressions.
- Implement input validation for regular expressions.
- Configure timeouts for regular expression operations.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
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The following list is the news that have been mention
CVE-2026-80206 vulnerability anywhere in the article.