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VulnerabilityPublished Updated

CVE-2026-81726: NLTK · Model-artifact APIs bypass pathsec and touch files outside allowed roots

Affects nltkSource GCVE Database

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Authoritative record:CVE-2026-81726· High 8.3

Not known to be exploited · CVSS 8.3 High : upgrade to 3.10.4 soon.

Data as of 2 Nov 2026, 23:14 UTC

CVSS 4.0 base score
8.3High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (VulnCheck)CVSS 4.08.3
CNA (VulnCheck)CVSS 3.17.0
Patch
Available – fixed in 3.10.4
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:L/VA:L/SC:N/SI:N/SA:N

Exploitation evidence

t = 0 is the CVE’s publication on cve.org

  1. Disclosed: evidence found.

    CVE published 27 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: evidence found.

    CISA SSVC: proof of concept public

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

Timeline

  1. CVE ID reserved

    by VulnCheck

    , 4 hours before disclosure

  2. CVE published

    on cve.org

    , t = 0

  3. CISA SSVC assessment

    proof of concept public

    , 5 hours after disclosure

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CISA SSVC, the Metasploit, Exploit-DB and nuclei-templates index as of 2 Nov 2026.

What to do

Upgrade nltk to 3.10.4.

Affected software

ProductAffectedFixed in
PyPInltkAffected
  • <3.10.4
Fixed in
  • 3.10.4

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A patch is available in NLTK version 3.10.4 that fixes this vulnerability by ensuring all model-path file accesses use pathsec.open() or equivalent pathsec-aware helpers. Users should upgrade to version 3.10.4 or later. Until then, avoid passing untrusted paths to the affected model-artifact APIs. No other mitigations are specified by the vendor advisory.

Description

NLTK versions prior to 3.10.4 contain a file sandbox bypass vulnerability in several model-artifact APIs. These APIs improperly handle caller-controlled model paths by using raw file operations instead of pathsec-aware helpers, allowing reading and writing of files outside the intended sandbox directories. This bypass undermines pathsec enforcement, potentially enabling unauthorized file access or modification. A fix is available in version 3.10.4.

References

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