CVE-2026-12243

HIGHPre-NVD 7.57.5—
EchelonGraph scoreHIGH confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-06-30. a secondary CVSS source baseline 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 7.5Exploit: NoneExposed: 0

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

NLTK version 3.9.4 is vulnerable to a path traversal attack due to an incomplete fix for GitHub Issue #3504. The _UNSAFE_NO_PROTOCOL_RE regex in nltk/data.py checks for literal ../ sequences but fails to account for percent-encoded traversal sequences such as ..%2f. The url2pathname() function decodes these sequences after the validation step, allowing an attacker to bypass the protection. This vulnerability enables an attacker to read arbitrary files accessible to the Python process by controlling the resource name parameter passed to nltk.data.load() or nltk.data.find(). The issue affects applications that rely on NLTK for resource loading, including NLP web applications, Jupyter notebooks, and CLI tools. The default pathsec.ENFORCE=False setting exacerbates the impact by not blocking the file read at the open() stage.

CVSS v3
7.5
EG Score
7.5(high)
EPSS
40.4%
KEV
Not listed

Published

June 30, 2026

Last Modified

June 30, 2026

Advisory Details (1)

Auto-updated Jun 30, 2026
No patch confirmed yet.
generic

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Vendor Advisories for CVE-2026-12243(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFixed inDependents
nltk0.8 ... 3.9b1 (65 versions)——

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 10× in last 7d / 58× 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. 2026-07-22 14:08 UTCEPSS rescore
  2. 2026-07-21 15:24 UTCEPSS rescore
  3. 2026-07-20 17:08 UTCEPSS rescore
  4. 2026-07-19 14:30 UTCEPSS rescore
  5. 2026-07-19 02:28 UTCEPSS rescore
  6. 2026-07-18 10:04 UTCEPSS rescore
  7. 2026-07-17 02:15 UTCGHSA enrichment
  8. 2026-07-16 17:02 UTCEPSS rescore
  9. 2026-07-16 12:43 UTCGHSA enrichment
  10. 2026-07-15 23:33 UTCGHSA enrichment
  11. 2026-07-15 16:57 UTCEPSS rescore
  12. 2026-07-15 10:25 UTCGHSA enrichment
  13. 2026-07-15 02:00 UTCEPSS rescore
  14. 2026-07-14 21:16 UTCGHSA enrichment
  15. 2026-07-14 08:07 UTCGHSA enrichment
  16. 2026-07-13 22:30 UTCEPSS rescore
  17. 2026-07-13 18:35 UTCGHSA enrichment
  18. 2026-07-13 06:12 UTCEPSS rescore
  19. 2026-07-13 05:26 UTCGHSA enrichment
  20. 2026-07-12 16:17 UTCGHSA enrichment
  21. 2026-07-12 05:46 UTCEPSS rescore
  22. 2026-07-12 03:08 UTCGHSA enrichment
  23. 2026-07-11 13:56 UTCGHSA enrichment
  24. 2026-07-11 08:27 UTCEPSS rescore
  25. 2026-07-11 00:46 UTCGHSA enrichment
Show 33 more
  1. 2026-07-10 11:36 UTCGHSA enrichment
  2. 2026-07-09 22:25 UTCGHSA enrichment
  3. 2026-07-09 19:10 UTCEPSS rescore
  4. 2026-07-09 09:15 UTCGHSA enrichment
  5. 2026-07-08 20:07 UTCGHSA enrichment
  6. 2026-07-08 15:15 UTCEPSS rescore
  7. 2026-07-08 15:15 UTCEPSS rescore
  8. 2026-07-08 06:57 UTCGHSA enrichment
  9. 2026-07-07 17:47 UTCGHSA enrichment
  10. 2026-07-07 13:46 UTCEPSS rescore
  11. 2026-07-07 04:17 UTCGHSA enrichment
  12. 2026-07-06 16:27 UTCEPSS rescore
  13. 2026-07-06 15:05 UTCGHSA enrichment
  14. 2026-07-06 02:23 UTCEPSS rescore
  15. 2026-07-06 01:54 UTCGHSA enrichment
  16. 2026-07-05 12:44 UTCGHSA enrichment
  17. 2026-07-05 02:30 UTCEPSS rescore
  18. 2026-07-05 02:30 UTCEPSS rescore
  19. 2026-07-04 23:35 UTCGHSA enrichment
  20. 2026-07-04 10:26 UTCGHSA enrichment
  21. 2026-07-04 06:31 UTCEPSS rescore
  22. 2026-07-03 21:17 UTCGHSA enrichment
  23. 2026-07-03 08:08 UTCGHSA enrichment
  24. 2026-07-02 18:59 UTCGHSA enrichment
  25. 2026-07-02 05:50 UTCGHSA enrichment
  26. 2026-07-01 16:40 UTCGHSA enrichment
  27. 2026-07-01 15:06 UTCEPSS rescore
  28. 2026-07-01 15:06 UTCEPSS rescore
  29. 2026-07-01 03:31 UTCGHSA enrichment
  30. 2026-06-30 23:22 UTCEPSS rescore
  31. 2026-06-30 14:22 UTCGHSA enrichment
  32. 2026-06-30 01:11 UTCEG score recompute
  33. 2026-06-30 01:10 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-12243?
CVE-2026-12243 is a high vulnerability published on June 30, 2026. NLTK version 3.9.4 is vulnerable to a path traversal attack due to an incomplete fix for GitHub Issue #3504. The UNSAFENOPROTOCOLRE regex in nltk/data.py checks for literal ../ sequences but fails to account for percent-encoded traversal sequences such as ..%2f. The url2pathname() function decodes…
When was CVE-2026-12243 disclosed?
CVE-2026-12243 was first published in the National Vulnerability Database on June 30, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-12243 actively exploited?
CVE-2026-12243 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 40.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-12243?
CVE-2026-12243 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-12243?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-12243, 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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