CVE-2026-78683

CRITICALPre-NVD 9.69.6
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

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, GitHub Security Advisory, a secondary CVSS source
Elevated
9.6EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.5%CVSS: 9.6Exploit: No code on recordExposed services: Not assessed

A fix is available — apply it.

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
9.6CRITICALmedium confidence
EG Risk
59
EG Risk 59/100

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 (value × EchelonGraph’s weight)
Severity96% × 45%
The EG Score, 9.6 of 10.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low, Track* at medium and Attend at high mission impact.
Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
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
0.5%
EPSS %ILE
41st
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track at low, Track* at medium and Attend at high mission impact.

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 no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

August 25, 2026

Last Modified

October 12, 2026

Advisory Details (2)

Auto-updated Oct 7, 2026
Patch available. Sources: github.
GitHub advisoryMentions a patch (unverified)

[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
Web page

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 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
nltk3.9.1-2, 3.9.2-1, 3.9.3-1
  • every version up to 3.10.0-1: fixed in 3.10.0-1
—
PyPI(1)
PackageVulnerable rangeFix by version rangeDependents
nltk0.8 ... 3.9b1 (65 versions)
  • every version up to 3.10.0: fixed in 3.10.0
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 16× in last 7d / 58× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 97 of 143 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 3 repeat rows among the latest 100 are merged into the row they repeat. The 46 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-13 19:05 UTCEG score recompute
  2. 2026-10-13 16:35 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  3. 2026-10-12 17:25 UTCEG score recompute
  4. 2026-10-12 16:35 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  5. 2026-10-12 15:36 UTCEG score recompute
  6. 2026-10-11 19:22 UTCEG score recompute
  7. 2026-10-11 16:38 UTCEG score recompute
  8. 2026-10-11 13:57 UTCEG score recompute
  9. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  10. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  11. 2026-10-10 12:24 UTCEG score recompute
  12. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  13. 2026-10-09 04:36 UTCEG score recompute
  14. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  15. 2026-10-08 03:39 UTCEG score recompute
  16. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  17. 2026-10-06 16:09 UTCEG score recompute
  18. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  19. 2026-10-05 18:02 UTCEG score recompute
  20. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  21. 2026-10-05 01:25 UTCEG score recompute
  22. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  23. 2026-10-03 16:28 UTCEG score recompute
  24. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  25. 2026-10-02 19:23 UTCEG score recompute
Show 72 more
  1. 2026-10-01 20:59 UTCEG score recompute
  2. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  3. 2026-09-30 20:16 UTCEG score recompute
  4. 2026-09-30 06:55 UTCEG score recompute
  5. 2026-09-29 15:24 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  6. 2026-09-28 21:31 UTCEG score recompute
  7. 2026-09-28 13:52 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  8. 2026-09-27 15:41 UTCEG score recompute
  9. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  10. 2026-09-26 22:11 UTCEG score recompute
  11. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  12. 2026-09-26 00:28 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  13. 2026-09-24 18:53 UTCEG score recompute
  14. 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  15. 2026-09-24 04:50 UTCEG score recompute
  16. 2026-09-23 20:31 UTCEG score recompute
  17. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  18. 2026-09-22 19:22 UTCEG score recompute
  19. 2026-09-22 16:01 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  20. 2026-09-21 22:30 UTCEG score recompute
  21. 2026-09-21 21:09 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  22. 2026-09-20 21:15 UTCEG score recompute
  23. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  24. 2026-09-19 19:23 UTCEG score recompute
  25. 2026-09-18 22:05 UTCEG score recompute
  26. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  27. 2026-09-17 21:10 UTCEG score recompute
  28. 2026-09-16 14:15 UTCEG score recompute
  29. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  30. 2026-09-16 09:25 UTCEG score recompute
  31. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  32. 2026-09-15 05:41 UTCEG score recompute
  33. 2026-09-15 03:12 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  34. 2026-09-13 19:51 UTCEG score recompute
  35. 2026-09-12 18:55 UTCEG score recompute
  36. 2026-09-11 13:46 UTCEG score recompute
  37. 2026-09-10 12:49 UTCEG score recompute
  38. 2026-09-09 01:19 UTCEG score recompute
  39. 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  40. 2026-09-07 19:42 UTCEG score recompute
  41. 2026-09-06 14:35 UTCEG score recompute
  42. 2026-09-06 13:48 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  43. 2026-09-05 17:43 UTCEG score recompute
  44. 2026-09-04 15:35 UTCEG score recompute
  45. 2026-09-04 07:10 UTCEG score recompute
  46. 2026-09-04 05:07 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  47. 2026-09-02 20:45 UTCEG score recompute
  48. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  49. 2026-09-02 14:08 UTCGHSA enrichmentGHSA-gx65-c5hj-vpv5 · GitHub severity CRITICAL · GitHub CVSS 9.6
  50. 2026-09-02 09:50 UTCGHSA enrichmentGHSA-gx65-c5hj-vpv5 · GitHub severity CRITICAL · GitHub CVSS 9.6
  51. 2026-09-02 05:40 UTCGHSA enrichmentGHSA-gx65-c5hj-vpv5 · GitHub severity CRITICAL · GitHub CVSS 9.6
  52. 2026-09-02 01:27 UTCGHSA enrichmentGHSA-gx65-c5hj-vpv5 · GitHub severity CRITICAL · GitHub CVSS 9.6
  53. 2026-09-01 21:16 UTCGHSA enrichmentGHSA-gx65-c5hj-vpv5 · GitHub severity CRITICAL · GitHub CVSS 9.6
  54. 2026-09-01 17:07 UTCEG score recompute
  55. 2026-09-01 17:07 UTCGHSA enrichmentGHSA-gx65-c5hj-vpv5 · GitHub severity CRITICAL · GitHub CVSS 9.6
  56. 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  57. 2026-09-01 12:40 UTCGHSA enrichmentGHSA-gx65-c5hj-vpv5 · GitHub severity CRITICAL · GitHub CVSS 9.6
  58. 2026-09-01 08:15 UTCEG score recompute
  59. 2026-09-01 08:14 UTCGHSA enrichmentGHSA-gx65-c5hj-vpv5 · GitHub severity CRITICAL · GitHub CVSS 9.6
  60. 2026-09-01 04:40 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  61. 2026-09-01 03:59 UTCGHSA enrichmentGHSA-gx65-c5hj-vpv5 · GitHub severity CRITICAL · GitHub CVSS 9.6
  62. 2026-08-31 23:24 UTCGHSA enrichmentGHSA-gx65-c5hj-vpv5 · GitHub severity CRITICAL · GitHub CVSS 9.6
  63. 2026-08-31 19:14 UTCGHSA enrichmentGHSA-gx65-c5hj-vpv5 · GitHub severity CRITICAL · GitHub CVSS 9.6
  64. 2026-08-31 17:41 UTCGHSA enrichmentGHSA-gx65-c5hj-vpv5 · GitHub severity CRITICAL · GitHub CVSS 9.6
  65. 2026-08-31 11:15 UTCGHSA enrichmentGHSA-gx65-c5hj-vpv5 · GitHub severity CRITICAL · GitHub CVSS 9.6
  66. 2026-08-31 07:00 UTCGHSA enrichmentGHSA-gx65-c5hj-vpv5 · GitHub severity CRITICAL · GitHub CVSS 9.6
  67. 2026-08-31 02:50 UTCGHSA enrichmentGHSA-gx65-c5hj-vpv5 · GitHub severity CRITICAL · GitHub CVSS 9.6
  68. 2026-08-30 22:41 UTCEG score recompute
  69. 2026-08-30 22:41 UTCGHSA enrichmentGHSA-gx65-c5hj-vpv5 · GitHub severity CRITICAL · GitHub CVSS 9.6
  70. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  71. 2026-08-30 18:32 UTCGHSA enrichmentGHSA-gx65-c5hj-vpv5 · GitHub severity CRITICAL · GitHub CVSS 9.6
  72. 2026-08-30 14:22 UTCGHSA enrichmentGHSA-gx65-c5hj-vpv5 · GitHub severity CRITICAL · GitHub CVSS 9.6

Related CVEs(same product + same CWE)

Frequently asked(5)

What is CVE-2026-78683?
CVE-2026-78683 is a critical-severity vulnerability; its CVE record was 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 made public?
CVE-2026-78683 was made public on August 11, 2026: that is the date its CVE record's CNA, VulnCheck, gives for when the vulnerability was made public. The CVE record itself was published on August 25, 2026. EchelonGraph's copy of the record carries a last-modified date of October 12, 2026; the record at its source may have been updated since.
Is CVE-2026-78683 actively exploited?
CVE-2026-78683 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (41st percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-78683?
CVE-2026-78683 has a CVSS base score of 9.6 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-78683?
A fix for CVE-2026-78683 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-78683 are linked in the Vendor Advisories panel on this page.

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