CVE-2026-72818

HIGHPre-NVD 7.57.5—
EchelonGraph scoreHIGH confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-08-21. the CNA's CVSS baseline 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:vulncheck, epss, ghsa
Elevated
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 7.5Exploit: Elevated riskExposed: 0

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

The URLS regular expression in nltk/tokenize/casual.py, compiled into TweetTokenizer.WORD_RE and applied by TweetTokenizer.tokenize, contains a naked-domain branch whose domain-label prefix [a-z0-9]+(?:[.\-][a-z0-9]+)* is unbounded. Input consisting of many alternating label separators can be partitioned in exponentially many ways, and because the branch also requires a trailing top-level domain that such input never supplies, the engine explores those partitions before failing at each offset. A few kilobytes of input therefore consumes seconds to minutes of single-threaded CPU, and the HANG_RE substitution performed before matching does not collapse the pattern. TweetTokenizer is intended for tokenizing untrusted social-media text, so any service that applies it, or the module-level casual_tokenize, to submitted text can be stalled per request without authentication. Version 3.10.1 bounds the label repetition.

CVSS v3
7.5
EG Score
7.5(high)
EG Risk
65(Attend)
EG Risk 65/100SSVC: Attend

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
Severity75% × 45%
Exploitation40% × 40%
Automatability100% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
1%
EPSS %ILE
42%
KEV
Not listed

Published

August 20, 2026

Last Modified

August 21, 2026

Advisory Details (4)

Auto-updated Aug 20, 2026
No patch confirmed yet.
generic

NLTK TweetTokenizer URL Pattern Backtracks Catastrophically on Naked-Domain-Like Input | Advisories | VulnCheck

https://www.vulncheck.com/advisories/nltk-tweettokenizer-url-pattern-backtracks-catastrophically-on-naked-domain-like-input
generic

ReDoS (catastrophic backtracking) in `TweetTokenizer` URL regex (naked-domain branch) · Issue #3704 · nltk/nltk · GitHub

https://github.com/nltk/nltk/issues/3704
generic

nltk/nltk/tokenize/casual.py at 3.9.4 · nltk/nltk · GitHub

https://github.com/nltk/nltk/blob/3.9.4/nltk/tokenize/casual.py
generic

GitHub - nltk/nltk: NLTK Source · GitHub

https://github.com/nltk/nltk

Vendor Advisories for CVE-2026-72818(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 (66 versions)3.10.1—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 11× in last 7d / 81× 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. 2026-09-19 04:35 UTCEG score recompute
  2. 2026-09-18 19:28 UTCEPSS rescore
  3. 2026-09-18 03:35 UTCEG score recompute
  4. 2026-09-16 14:43 UTCEG score recompute
  5. 2026-09-16 14:08 UTCEPSS rescore
  6. 2026-09-16 05:15 UTCEPSS rescore
  7. 2026-09-15 14:41 UTCEG score recompute
  8. 2026-09-15 03:12 UTCEPSS rescore
  9. 2026-09-14 02:33 UTCEG score recompute
  10. 2026-09-13 02:31 UTCEG score recompute
  11. 2026-09-12 15:02 UTCEPSS rescore
  12. 2026-09-12 02:29 UTCEG score recompute
  13. 2026-09-11 14:53 UTCEPSS rescore
  14. 2026-09-11 14:28 UTCEG score recompute
  15. 2026-09-10 14:26 UTCEG score recompute
  16. 2026-09-10 09:35 UTCEPSS rescore
  17. 2026-09-09 01:51 UTCEG score recompute
  18. 2026-09-08 22:01 UTCEPSS rescore
  19. 2026-09-08 03:31 UTCEG score recompute
  20. 2026-09-06 14:51 UTCEG score recompute
  21. 2026-09-06 13:48 UTCEPSS rescore
  22. 2026-09-06 02:50 UTCEG score recompute
  23. 2026-09-04 14:35 UTCEG score recompute
  24. 2026-09-04 05:07 UTCEPSS rescore
  25. 2026-09-02 14:22 UTCEG score recompute
Show 56 more
  1. 2026-09-02 14:21 UTCGHSA enrichment
  2. 2026-09-02 14:12 UTCEPSS rescore
  3. 2026-09-02 02:18 UTCGHSA enrichment
  4. 2026-09-01 14:14 UTCEG score recompute
  5. 2026-09-01 14:14 UTCGHSA enrichment
  6. 2026-09-01 13:54 UTCEPSS rescore
  7. 2026-09-01 04:40 UTCEPSS rescore
  8. 2026-09-01 04:40 UTCEPSS rescore
  9. 2026-09-01 02:13 UTCGHSA enrichment
  10. 2026-08-31 14:07 UTCGHSA enrichment
  11. 2026-08-31 01:33 UTCEG score recompute
  12. 2026-08-31 01:33 UTCGHSA enrichment
  13. 2026-08-30 19:18 UTCEPSS rescore
  14. 2026-08-30 19:17 UTCEPSS rescore
  15. 2026-08-30 13:32 UTCGHSA enrichment
  16. 2026-08-30 01:31 UTCEG score recompute
  17. 2026-08-30 01:31 UTCGHSA enrichment
  18. 2026-08-30 01:22 UTCEPSS rescore
  19. 2026-08-29 13:30 UTCGHSA enrichment
  20. 2026-08-29 01:18 UTCEG score recompute
  21. 2026-08-29 01:18 UTCGHSA enrichment
  22. 2026-08-28 21:42 UTCEPSS rescore
  23. 2026-08-28 11:44 UTCGHSA enrichment
  24. 2026-08-27 23:43 UTCEG score recompute
  25. 2026-08-27 23:43 UTCGHSA enrichment
  26. 2026-08-27 14:25 UTCEPSS rescore
  27. 2026-08-27 11:42 UTCGHSA enrichment
  28. 2026-08-26 23:41 UTCEG score recompute
  29. 2026-08-26 23:41 UTCGHSA enrichment
  30. 2026-08-26 14:47 UTCEPSS rescore
  31. 2026-08-26 11:39 UTCGHSA enrichment
  32. 2026-08-25 23:38 UTCEG score recompute
  33. 2026-08-25 23:38 UTCGHSA enrichment
  34. 2026-08-25 13:49 UTCEPSS rescore
  35. 2026-08-25 11:37 UTCGHSA enrichment
  36. 2026-08-24 23:36 UTCEG score recompute
  37. 2026-08-24 23:36 UTCGHSA enrichment
  38. 2026-08-24 11:35 UTCEG score recompute
  39. 2026-08-24 11:35 UTCGHSA enrichment
  40. 2026-08-23 23:34 UTCGHSA enrichment
  41. 2026-08-23 11:34 UTCEG score recompute
  42. 2026-08-23 11:34 UTCGHSA enrichment
  43. 2026-08-23 00:19 UTCEPSS rescore
  44. 2026-08-22 23:33 UTCGHSA enrichment
  45. 2026-08-22 11:32 UTCEG score recompute
  46. 2026-08-22 11:32 UTCGHSA enrichment
  47. 2026-08-21 23:49 UTCEPSS rescore
  48. 2026-08-21 23:31 UTCGHSA enrichment
  49. 2026-08-21 11:30 UTCEG score recompute
  50. 2026-08-21 11:30 UTCGHSA enrichment
  51. 2026-08-21 11:19 UTCEG score recompute
  52. 2026-08-21 11:18 UTCGHSA enrichment
  53. 2026-08-20 23:42 UTCEG score recompute
  54. 2026-08-20 22:23 UTCEG score recompute
  55. 2026-08-20 22:07 UTCEG score recompute
  56. 2026-08-20 22:07 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-72818?
CVE-2026-72818 is a high vulnerability published on August 20, 2026. The URLS regular expression in nltk/tokenize/casual.py, compiled into TweetTokenizer.WORDRE and applied by TweetTokenizer.tokenize, contains a naked-domain branch whose domain-label prefix [a-z0-9]+(?:[.\-][a-z0-9]+)* is unbounded. Input consisting of many alternating label separators can be…
When was CVE-2026-72818 disclosed?
CVE-2026-72818 was first published in the National Vulnerability Database on August 20, 2026, with the most recent update on August 21, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-72818 actively exploited?
CVE-2026-72818 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 57.9% of all scored CVEs.
What is the CVSS score of CVE-2026-72818?
CVE-2026-72818 has a CVSS v4.0 base score of 7.5 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-72818?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-72818, 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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