CVE-2026-72818

HIGHPre-NVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-08-21. A secondary CVSS source baseline 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
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: 0.7%CVSS: 7.5Exploit: Elevated riskExposed services: Not assessed

A fix is available — apply it.

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
7.5HIGHmedium confidence
EG Risk
65
EG Risk 65/100CISA SSVC

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%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.7%
EPSS %ILE
53rd
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

August 20, 2026

Last Modified

September 24, 2026

Advisory Details (4)

Auto-updated Aug 20, 2026
Patch available.
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 rangeFix by version rangeDependents
nltk3.10.0-1 ... 3.9.3-1 (9 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
nltk3.10.0-1 ... 3.9.3-1 (6 versions)
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
nltk3.10.0-1, 3.10.1-1, 3.9.1-2, 3.9.2-1, 3.9.3-1
  • every version up to 3.10.3-1: fixed in 3.10.3-1
—
PyPI(1)
PackageVulnerable rangeFix by version rangeDependents
nltk0.8 ... 3.9b1 (66 versions)
  • every version up to 3.10.1: fixed in 3.10.1
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 8× in last 7d / 47× 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.

Showing the most recent 100 of 106 total refreshes for this CVE.

  1. 2026-10-03 16:44 UTCEG score recompute
  2. 2026-10-03 14:26 UTCEPSS rescore
  3. 2026-10-02 21:35 UTCEG score recompute
  4. 2026-10-01 21:26 UTCEG score recompute
  5. 2026-10-01 19:50 UTCEPSS rescore
  6. 2026-09-30 20:30 UTCEG score recompute
  7. 2026-09-30 08:05 UTCEG score recompute
  8. 2026-09-29 02:54 UTCEG score recompute
  9. 2026-09-28 14:53 UTCEG score recompute
  10. 2026-09-28 13:52 UTCEPSS rescore
  11. 2026-09-27 14:49 UTCEG score recompute
  12. 2026-09-27 13:48 UTCEPSS rescore
  13. 2026-09-27 02:48 UTCEG score recompute
  14. 2026-09-26 15:59 UTCEPSS rescore
  15. 2026-09-24 20:15 UTCEG score recompute
  16. 2026-09-24 14:58 UTCEG score recompute
  17. 2026-09-23 20:02 UTCEG score recompute
  18. 2026-09-23 17:54 UTCEPSS rescore
  19. 2026-09-22 19:44 UTCEG score recompute
  20. 2026-09-22 05:52 UTCEG score recompute
  21. 2026-09-21 21:09 UTCEPSS rescore
  22. 2026-09-21 05:46 UTCEG score recompute
  23. 2026-09-20 20:16 UTCEPSS rescore
  24. 2026-09-20 04:37 UTCEG score recompute
  25. 2026-09-19 16:36 UTCEG score recompute
Show 75 more
  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
  26. 2026-09-02 14:21 UTCGHSA enrichment
  27. 2026-09-02 14:12 UTCEPSS rescore
  28. 2026-09-02 02:18 UTCGHSA enrichment
  29. 2026-09-01 14:14 UTCEG score recompute
  30. 2026-09-01 14:14 UTCGHSA enrichment
  31. 2026-09-01 13:54 UTCEPSS rescore
  32. 2026-09-01 04:40 UTCEPSS rescore
  33. 2026-09-01 04:40 UTCEPSS rescore
  34. 2026-09-01 02:13 UTCGHSA enrichment
  35. 2026-08-31 14:07 UTCGHSA enrichment
  36. 2026-08-31 01:33 UTCEG score recompute
  37. 2026-08-31 01:33 UTCGHSA enrichment
  38. 2026-08-30 19:18 UTCEPSS rescore
  39. 2026-08-30 19:17 UTCEPSS rescore
  40. 2026-08-30 13:32 UTCGHSA enrichment
  41. 2026-08-30 01:31 UTCEG score recompute
  42. 2026-08-30 01:31 UTCGHSA enrichment
  43. 2026-08-30 01:22 UTCEPSS rescore
  44. 2026-08-29 13:30 UTCGHSA enrichment
  45. 2026-08-29 01:18 UTCEG score recompute
  46. 2026-08-29 01:18 UTCGHSA enrichment
  47. 2026-08-28 21:42 UTCEPSS rescore
  48. 2026-08-28 11:44 UTCGHSA enrichment
  49. 2026-08-27 23:43 UTCEG score recompute
  50. 2026-08-27 23:43 UTCGHSA enrichment
  51. 2026-08-27 14:25 UTCEPSS rescore
  52. 2026-08-27 11:42 UTCGHSA enrichment
  53. 2026-08-26 23:41 UTCEG score recompute
  54. 2026-08-26 23:41 UTCGHSA enrichment
  55. 2026-08-26 14:47 UTCEPSS rescore
  56. 2026-08-26 11:39 UTCGHSA enrichment
  57. 2026-08-25 23:38 UTCEG score recompute
  58. 2026-08-25 23:38 UTCGHSA enrichment
  59. 2026-08-25 13:49 UTCEPSS rescore
  60. 2026-08-25 11:37 UTCGHSA enrichment
  61. 2026-08-24 23:36 UTCEG score recompute
  62. 2026-08-24 23:36 UTCGHSA enrichment
  63. 2026-08-24 11:35 UTCEG score recompute
  64. 2026-08-24 11:35 UTCGHSA enrichment
  65. 2026-08-23 23:34 UTCGHSA enrichment
  66. 2026-08-23 11:34 UTCEG score recompute
  67. 2026-08-23 11:34 UTCGHSA enrichment
  68. 2026-08-23 00:19 UTCEPSS rescore
  69. 2026-08-22 23:33 UTCGHSA enrichment
  70. 2026-08-22 11:32 UTCEG score recompute
  71. 2026-08-22 11:32 UTCGHSA enrichment
  72. 2026-08-21 23:49 UTCEPSS rescore
  73. 2026-08-21 23:31 UTCGHSA enrichment
  74. 2026-08-21 11:30 UTCEG score recompute
  75. 2026-08-21 11:30 UTCGHSA enrichment

Related CVEs(same product + same CWE)

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 on August 20, 2026, with the most recent update on September 24, 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 0.7% probability of exploitation in the next 30 days (53rd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-72818?
CVE-2026-72818 has a CVSS base score of 7.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-72818?
A fix for CVE-2026-72818 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-72818 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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