CVE-2026-78683

CRITICALPre-NVD 9.69.6—
EchelonGraph scoreHIGH confidence

Score 9.6 from GitHub Security Advisory (severity: CRITICAL) published 2026-08-25. a secondary CVSS source baseline 9.6; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Elevated
9.6EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.6Exploit: Elevated riskExposed: 0

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

NLTK before 3.10.0 (affected versions <=3.9.4) contains an unsafe pickle deserialization vulnerability in the TransitionParser.parse() method (nltk/parse/transitionparser.py). The method calls pickle_load() with the default restricted=False, routing deserialization through WarningUnpickler, which does not override find_class() and therefore permits arbitrary class resolution. When an application loads an attacker-crafted model file, embedded pickle gadget chains execute arbitrary Python code with the privileges of the user running the application. NLTK provides a RestrictedUnpickler for safe deserialization, but it is not used by production code paths. Fixed in 3.10.0.

CVSS v3
9.6
EG Score
9.6(high)
EG Risk
59(Track*)
EG Risk 59/100SSVC: 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
Severity96% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Watch closely — could escalate to Attend.
EPSS PROB
0%
EPSS %ILE
22%
KEV
Not listed

Published

August 25, 2026

Last Modified

August 31, 2026

Advisory Details (2)

Auto-updated Sep 14, 2026
🔬 Proof of concept available. Patch available. Sources: github.
github Patch Available🟡 PoC Available

[CWE-502] Unsafe Pickle Deserialization in TransitionParser Allows Remote Code Execution · Advisory · nltk/nltk · GitHub

Affected: 3.10.0+.

https://github.com/nltk/nltk/security/advisories/GHSA-rhp5-r9x4-f5g2
generic

NLTK before 3.10.0 Remote Code Execution via Unsafe Pickle Deserialization | Advisories | VulnCheck

https://www.vulncheck.com/advisories/nltk-before-remote-code-execution-via-unsafe-pickle-deserialization

Vendor Advisories for CVE-2026-78683(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
nltk3.9.1-2, 3.9.2-1, 3.9.3-13.10.0-1—
PyPI(1)
PackageVulnerable rangeFixed inDependents
nltk0.8 ... 3.9b1 (65 versions)3.10.0—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 12× in last 7d / 97× 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 22:05 UTCEG score recompute
  2. 2026-09-18 19:28 UTCEPSS rescore
  3. 2026-09-17 21:10 UTCEG score recompute
  4. 2026-09-16 14:15 UTCEG score recompute
  5. 2026-09-16 14:08 UTCEPSS rescore
  6. 2026-09-16 09:25 UTCEG score recompute
  7. 2026-09-16 05:15 UTCEPSS rescore
  8. 2026-09-15 05:41 UTCEG score recompute
  9. 2026-09-15 03:12 UTCEPSS rescore
  10. 2026-09-15 03:12 UTCEPSS rescore
  11. 2026-09-13 19:51 UTCEG score recompute
  12. 2026-09-12 18:55 UTCEG score recompute
  13. 2026-09-11 13:46 UTCEG score recompute
  14. 2026-09-10 12:49 UTCEG score recompute
  15. 2026-09-09 01:19 UTCEG score recompute
  16. 2026-09-08 22:01 UTCEPSS rescore
  17. 2026-09-07 19:42 UTCEG score recompute
  18. 2026-09-06 14:35 UTCEG score recompute
  19. 2026-09-06 13:48 UTCEPSS rescore
  20. 2026-09-05 17:43 UTCEG score recompute
  21. 2026-09-04 15:35 UTCEG score recompute
  22. 2026-09-04 07:10 UTCEG score recompute
  23. 2026-09-04 05:07 UTCEPSS rescore
  24. 2026-09-02 20:45 UTCEG score recompute
  25. 2026-09-02 14:12 UTCEPSS rescore
Show 72 more
  1. 2026-09-02 14:08 UTCGHSA enrichment
  2. 2026-09-02 09:50 UTCGHSA enrichment
  3. 2026-09-02 05:40 UTCGHSA enrichment
  4. 2026-09-02 01:27 UTCGHSA enrichment
  5. 2026-09-01 21:16 UTCGHSA enrichment
  6. 2026-09-01 17:07 UTCEG score recompute
  7. 2026-09-01 17:07 UTCGHSA enrichment
  8. 2026-09-01 13:54 UTCEPSS rescore
  9. 2026-09-01 12:40 UTCGHSA enrichment
  10. 2026-09-01 08:15 UTCEG score recompute
  11. 2026-09-01 08:14 UTCGHSA enrichment
  12. 2026-09-01 04:40 UTCEPSS rescore
  13. 2026-09-01 04:40 UTCEPSS rescore
  14. 2026-09-01 03:59 UTCGHSA enrichment
  15. 2026-08-31 23:24 UTCGHSA enrichment
  16. 2026-08-31 19:14 UTCGHSA enrichment
  17. 2026-08-31 17:41 UTCGHSA enrichment
  18. 2026-08-31 11:15 UTCGHSA enrichment
  19. 2026-08-31 07:00 UTCGHSA enrichment
  20. 2026-08-31 02:50 UTCGHSA enrichment
  21. 2026-08-30 22:41 UTCEG score recompute
  22. 2026-08-30 22:41 UTCGHSA enrichment
  23. 2026-08-30 19:18 UTCEPSS rescore
  24. 2026-08-30 19:17 UTCEPSS rescore
  25. 2026-08-30 18:32 UTCGHSA enrichment
  26. 2026-08-30 14:22 UTCGHSA enrichment
  27. 2026-08-30 10:10 UTCGHSA enrichment
  28. 2026-08-30 06:01 UTCGHSA enrichment
  29. 2026-08-30 01:51 UTCEG score recompute
  30. 2026-08-30 01:51 UTCGHSA enrichment
  31. 2026-08-30 01:22 UTCEPSS rescore
  32. 2026-08-29 21:42 UTCGHSA enrichment
  33. 2026-08-29 17:32 UTCGHSA enrichment
  34. 2026-08-29 12:55 UTCGHSA enrichment
  35. 2026-08-29 08:44 UTCGHSA enrichment
  36. 2026-08-29 04:31 UTCGHSA enrichment
  37. 2026-08-29 00:18 UTCEG score recompute
  38. 2026-08-29 00:18 UTCGHSA enrichment
  39. 2026-08-28 21:42 UTCEPSS rescore
  40. 2026-08-28 19:08 UTCGHSA enrichment
  41. 2026-08-28 16:23 UTCGHSA enrichment
  42. 2026-08-28 11:51 UTCGHSA enrichment
  43. 2026-08-28 07:41 UTCGHSA enrichment
  44. 2026-08-28 03:30 UTCGHSA enrichment
  45. 2026-08-27 23:21 UTCGHSA enrichment
  46. 2026-08-27 19:12 UTCGHSA enrichment
  47. 2026-08-27 15:01 UTCGHSA enrichment
  48. 2026-08-27 10:51 UTCGHSA enrichment
  49. 2026-08-27 06:40 UTCGHSA enrichment
  50. 2026-08-27 02:05 UTCGHSA enrichment
  51. 2026-08-26 21:55 UTCGHSA enrichment
  52. 2026-08-26 17:46 UTCEG score recompute
  53. 2026-08-26 17:46 UTCGHSA enrichment
  54. 2026-08-26 14:47 UTCEPSS rescore
  55. 2026-08-26 13:18 UTCGHSA enrichment
  56. 2026-08-26 09:08 UTCGHSA enrichment
  57. 2026-08-26 04:55 UTCGHSA enrichment
  58. 2026-08-26 00:46 UTCGHSA enrichment
  59. 2026-08-25 20:37 UTCGHSA enrichment
  60. 2026-08-25 16:24 UTCEG score recompute
  61. 2026-08-25 16:24 UTCGHSA enrichment
  62. 2026-08-25 15:30 UTCEG score recompute
  63. 2026-08-25 15:30 UTCGHSA enrichment
  64. 2026-08-25 14:49 UTCEG score recompute
  65. 2026-08-25 14:49 UTCGHSA enrichment
  66. 2026-08-25 13:49 UTCEPSS rescore
  67. 2026-08-25 10:40 UTCGHSA enrichment
  68. 2026-08-25 06:30 UTCEG score recompute
  69. 2026-08-25 06:30 UTCGHSA enrichment
  70. 2026-08-25 02:19 UTCEG score recompute
  71. 2026-08-25 01:50 UTCEG score recompute
  72. 2026-08-25 01:50 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-78683?
CVE-2026-78683 is a critical vulnerability published on August 25, 2026. NLTK before 3.10.0 (affected versions <=3.9.4) contains an unsafe pickle deserialization vulnerability in the TransitionParser.parse() method (nltk/parse/transitionparser.py). The method calls pickleload() with the default restricted=False, routing deserialization through WarningUnpickler, which…
When was CVE-2026-78683 disclosed?
CVE-2026-78683 was first published in the National Vulnerability Database on August 25, 2026, with the most recent update on August 31, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-78683 actively exploited?
CVE-2026-78683 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 78.0% of all scored CVEs.
What is the CVSS score of CVE-2026-78683?
CVE-2026-78683 has a CVSS v3 base score of 9.6 (NVD).
How do I remediate CVE-2026-78683?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-78683, 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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