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
Trending — 4 sources updated this weekElevated
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
20%
KEV
Not listed

Published

August 25, 2026

Last Modified

August 28, 2026

Advisory Details (2)

Auto-updated Aug 28, 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.

Weakness Classification(1)

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

Data Freshness Timeline

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

Related CVEs(same CWE)

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 28, 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 80.4% 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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