CVE-2026-12261

MEDIUMPre-NVD 5.35.3—
EchelonGraph scoreHIGH confidence

Score 5.3 from GitHub Security Advisory published 2026-08-07. a secondary CVSS source baseline 5.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 3 sources updated this weekElevated
5.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.3Exploit: Elevated riskExposed: 0

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

A vulnerability in nltk.downloader in nltk/nltk versions <= 3.9.4 allows for cross-package resource and model poisoning. The downloader extracts package archives into shared namespaces such as corpora/ and taggers/ instead of package-isolated roots, and validates package integrity only after the archive has been written and extracted. This design flaw enables one package to overwrite another package's trusted resources within the same namespace, making the changes immediately active through ordinary NLTK APIs. This issue persists across fresh interpreter restarts and can affect downstream workflows, including machine learning pipelines and reproducibility-sensitive environments.

CVSS v3
5.3
EG Score
5.3(high)
EG Risk
40(Track)
EG Risk 40/100SSVC: 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
Severity53% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
9%
KEV
Not listed

Published

August 7, 2026

Last Modified

August 7, 2026

Advisory Details (1)

Auto-updated Aug 7, 2026
No patch confirmed yet.
generic

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Vendor Advisories for CVE-2026-12261(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 20× in last 7d / 43× 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. 2026-08-20 02:25 UTCEG score recompute
  2. 2026-08-20 02:25 UTCGHSA enrichment
  3. 2026-08-19 17:03 UTCEPSS rescore
  4. 2026-08-19 03:31 UTCEG score recompute
  5. 2026-08-19 03:31 UTCGHSA enrichment
  6. 2026-08-18 13:48 UTCEPSS rescore
  7. 2026-08-18 04:38 UTCEG score recompute
  8. 2026-08-18 04:38 UTCGHSA enrichment
  9. 2026-08-17 05:44 UTCEG score recompute
  10. 2026-08-17 05:44 UTCGHSA enrichment
  11. 2026-08-16 14:56 UTCEPSS rescore
  12. 2026-08-16 06:20 UTCEG score recompute
  13. 2026-08-16 06:19 UTCGHSA enrichment
  14. 2026-08-16 02:14 UTCEPSS rescore
  15. 2026-08-15 07:27 UTCEG score recompute
  16. 2026-08-15 07:27 UTCGHSA enrichment
  17. 2026-08-15 01:30 UTCEPSS rescore
  18. 2026-08-14 08:33 UTCEG score recompute
  19. 2026-08-14 08:33 UTCGHSA enrichment
  20. 2026-08-13 22:00 UTCEPSS rescore
  21. 2026-08-13 09:40 UTCEG score recompute
  22. 2026-08-13 09:40 UTCGHSA enrichment
  23. 2026-08-12 13:50 UTCEPSS rescore
  24. 2026-08-12 10:48 UTCEG score recompute
  25. 2026-08-12 10:48 UTCGHSA enrichment
Show 18 more
  1. 2026-08-11 13:42 UTCEPSS rescore
  2. 2026-08-11 11:54 UTCEG score recompute
  3. 2026-08-11 11:54 UTCGHSA enrichment
  4. 2026-08-10 23:59 UTCEPSS rescore
  5. 2026-08-10 13:01 UTCGHSA enrichment
  6. 2026-08-09 14:08 UTCEG score recompute
  7. 2026-08-09 14:08 UTCGHSA enrichment
  8. 2026-08-09 13:46 UTCEPSS rescore
  9. 2026-08-08 16:37 UTCEPSS rescore
  10. 2026-08-08 15:16 UTCEG score recompute
  11. 2026-08-08 15:16 UTCGHSA enrichment
  12. 2026-08-07 16:23 UTCEG score recompute
  13. 2026-08-07 16:23 UTCGHSA enrichment
  14. 2026-08-07 15:43 UTCEG score recompute
  15. 2026-08-07 15:43 UTCGHSA enrichment
  16. 2026-08-07 07:21 UTCEG score recompute
  17. 2026-08-07 06:38 UTCEG score recompute
  18. 2026-08-07 06:38 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-12261?
CVE-2026-12261 is a medium vulnerability published on August 7, 2026. A vulnerability in nltk.downloader in nltk/nltk versions <= 3.9.4 allows for cross-package resource and model poisoning. The downloader extracts package archives into shared namespaces such as corpora/ and taggers/ instead of package-isolated roots, and validates package integrity only after the…
When was CVE-2026-12261 disclosed?
CVE-2026-12261 was first published in the National Vulnerability Database on August 7, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-12261 actively exploited?
CVE-2026-12261 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 90.8% of all scored CVEs.
What is the CVSS score of CVE-2026-12261?
CVE-2026-12261 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2026-12261?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-12261, 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

Explore the affected products and dependency analysis for CVE-2026-12261

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