CVE-2026-80206

MEDIUMPre-NVD 5.95.9—
EchelonGraph scoreHIGH confidence

Score 5.9 from GitHub Security Advisory (severity: HIGH) published 2026-08-31. a secondary CVSS source baseline 5.9; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Elevated
5.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.9Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
5.9
EG Score
5.9(high)
EG Risk
43(Track)
EG Risk 43/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity59% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
19%
KEV
Not listed

Published

August 26, 2026

Last Modified

September 1, 2026

Advisory Details (2)

Auto-updated Aug 26, 2026
🔬 Proof of concept available. Patch available. Sources: github.
generic

NLTK 3.10.2 Regular Expression Denial of Service via tgrep | Advisories | VulnCheck

https://www.vulncheck.com/advisories/nltk-3.10.2-regular-expression-denial-of-service-via-tgrep
github Patch Available🟡 PoC Available

ReDoS in nltk.tgrep via unvalidated user-supplied regular expressions · Advisory · nltk/nltk · GitHub

https://github.com/nltk/nltk/security/advisories/GHSA-w3v8-gmh9-3wv7

Vendor Advisories for CVE-2026-80206(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(4 across 4 ecosystems)
Debian:12(1)
PackageVulnerable rangeFixed inDependents
nltk3.10.0-1 ... 3.9.3-1 (9 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
nltk3.10.0-1 ... 3.9.3-1 (6 versions)——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
nltk3.10.0-1, 3.10.1-1, 3.9.1-2, 3.9.2-1, 3.9.3-13.10.3-1—
PyPI(1)
PackageVulnerable rangeFixed inDependents
nltk0.8 ... 3.9b1 (68 versions)3.10.3—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 10× in last 7d / 43× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-09-18 19:28 UTCEPSS rescore
  2. 2026-09-18 06:58 UTCEG score recompute
  3. 2026-09-17 04:54 UTCEG score recompute
  4. 2026-09-16 14:08 UTCEPSS rescore
  5. 2026-09-16 05:15 UTCEPSS rescore
  6. 2026-09-16 02:49 UTCEG score recompute
  7. 2026-09-15 03:12 UTCEPSS rescore
  8. 2026-09-15 03:12 UTCEPSS rescore
  9. 2026-09-13 22:41 UTCEG score recompute
  10. 2026-09-12 20:37 UTCEG score recompute
  11. 2026-09-11 18:33 UTCEG score recompute
  12. 2026-09-11 14:53 UTCEPSS rescore
  13. 2026-09-11 14:53 UTCEPSS rescore
  14. 2026-09-10 16:28 UTCEG score recompute
  15. 2026-09-09 13:53 UTCEG score recompute
  16. 2026-09-08 22:01 UTCEPSS rescore
  17. 2026-09-08 11:27 UTCEG score recompute
  18. 2026-09-07 06:54 UTCEG score recompute
  19. 2026-09-06 13:48 UTCEPSS rescore
  20. 2026-09-06 04:44 UTCEG score recompute
  21. 2026-09-05 15:31 UTCEPSS rescore
  22. 2026-09-05 02:40 UTCEG score recompute
  23. 2026-09-04 05:07 UTCEPSS rescore
  24. 2026-09-02 22:25 UTCEG score recompute
  25. 2026-09-02 14:12 UTCEPSS rescore
Show 18 more
  1. 2026-09-01 20:21 UTCEG score recompute
  2. 2026-09-01 20:21 UTCGHSA enrichment
  3. 2026-09-01 13:54 UTCEPSS rescore
  4. 2026-09-01 04:40 UTCEPSS rescore
  5. 2026-09-01 04:40 UTCEPSS rescore
  6. 2026-08-31 04:11 UTCEG score recompute
  7. 2026-08-30 19:18 UTCEPSS rescore
  8. 2026-08-30 19:17 UTCEPSS rescore
  9. 2026-08-30 02:03 UTCEG score recompute
  10. 2026-08-30 01:22 UTCEPSS rescore
  11. 2026-08-28 23:58 UTCEG score recompute
  12. 2026-08-28 21:42 UTCEPSS rescore
  13. 2026-08-27 18:07 UTCEG score recompute
  14. 2026-08-27 14:25 UTCEPSS rescore
  15. 2026-08-26 15:53 UTCEG score recompute
  16. 2026-08-26 12:58 UTCEG score recompute
  17. 2026-08-26 10:48 UTCEG score recompute
  18. 2026-08-26 10:47 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-80206?
CVE-2026-80206 is a medium vulnerability published on August 26, 2026. NLTK before 3.10.3 contains a regular expression denial of service (ReDoS) vulnerability in the tgrep module. The tgrepnodeaction 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…
When was CVE-2026-80206 disclosed?
CVE-2026-80206 was first published in the National Vulnerability Database on August 26, 2026, with the most recent update on September 1, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-80206 actively exploited?
CVE-2026-80206 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 81.4% of all scored CVEs.
What is the CVSS score of CVE-2026-80206?
CVE-2026-80206 has a CVSS v3 base score of 5.9 (NVD).
How do I remediate CVE-2026-80206?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-80206, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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