CVE-2026-81727

HIGHPre-NVD 7.17.1—
EchelonGraph scoreHIGH confidence

Score 7.1 from GitHub Security Advisory published 2026-08-27. a secondary CVSS source baseline 7.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 4 sources updated this week
7.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.1Exploit: None knownExposed: 0

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

NLTK versions before 3.10.3 contain a filesystem containment bypass vulnerability in the Downloader.download and Downloader.incr_download methods that allows attackers to overwrite files outside the install root through pre-existing hardlinks. Attackers with write access to a shared downloader directory can create hardlinks pointing to outside-root files that are then overwritten during normal package extraction, mutating files outside the intended install tree.

CVSS v3
7.1
EG Score
7.1(high)
EG Risk
37(Track)
EG Risk 37/100SSVC: 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
Severity71% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
3%
KEV
Not listed

Published

August 27, 2026

Last Modified

August 28, 2026

Advisory Details (2)

Auto-updated Aug 27, 2026
🔬 Proof of concept available. Patch available. Sources: github.
generic

NLTK before 3.10.3 Hardlink File Overwrite via downloader | Advisories | VulnCheck

https://www.vulncheck.com/advisories/nltk-before-3.10.3-hardlink-file-overwrite-via-downloader
github Patch Available🟡 PoC Available

Downloader.download follows hardlinks and overwrites outside-root files · Advisory · nltk/nltk · GitHub

https://github.com/nltk/nltk/security/advisories/GHSA-f794-5jv7-7672

Vendor Advisories for CVE-2026-81727(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 12× in last 7d / 12× 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. 2026-08-30 01:22 UTCEPSS rescore
  2. 2026-08-29 20:37 UTCGHSA enrichment
  3. 2026-08-29 07:50 UTCEG score recompute
  4. 2026-08-29 07:49 UTCGHSA enrichment
  5. 2026-08-28 21:42 UTCEPSS rescore
  6. 2026-08-28 19:03 UTCGHSA enrichment
  7. 2026-08-28 09:14 UTCGHSA enrichment
  8. 2026-08-27 20:27 UTCEG score recompute
  9. 2026-08-27 20:27 UTCGHSA enrichment
  10. 2026-08-27 17:24 UTCEG score recompute
  11. 2026-08-27 16:47 UTCEG score recompute
  12. 2026-08-27 16:43 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-81727?
CVE-2026-81727 is a high vulnerability published on August 27, 2026. NLTK versions before 3.10.3 contain a filesystem containment bypass vulnerability in the Downloader.download and Downloader.incr_download methods that allows attackers to overwrite files outside the install root through pre-existing hardlinks. Attackers with write access to a shared downloader…
When was CVE-2026-81727 disclosed?
CVE-2026-81727 was first published in the National Vulnerability Database on August 27, 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-2026-81727 actively exploited?
CVE-2026-81727 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 96.6% of all scored CVEs.
What is the CVSS score of CVE-2026-81727?
CVE-2026-81727 has a CVSS v3 base score of 7.1 (NVD).
How do I remediate CVE-2026-81727?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-81727, 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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