CVE-2026-81726: NLTK · Model-artifact APIs bypass pathsec and touch files outside allowed roots
Affects nltkSource GCVE Database
Not known to be exploited · CVSS 8.3 High : upgrade to 3.10.4 soon.
Data as of 2 Nov 2026, 23:14 UTC
Thin evidence
One scorer or none| CNA (VulnCheck) | CVSS 4.0 | 8.3 |
|---|---|---|
| CNA (VulnCheck) | CVSS 3.1 | 7.0 |
- 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:NExploitation evidence
t = 0 is the CVE’s publication on cve.org
Disclosed: evidence found.
CVE published 27 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: evidence found.
CISA SSVC: proof of concept public
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
Timeline
CVE ID reserved
by VulnCheck
, 4 hours before disclosure
CVE published
on cve.org
, t = 0
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
| Product | Affected | Fixed in |
|---|---|---|
| PyPInltk | Affected
| Fixed in
|
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
- github.com/nltk/nltk/security/advisories/GHSA-8mgp-746c-j5xp (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2026-81726 (opens in a new tab)
- github.com/nltk/nltk/pull/3757 (opens in a new tab)
- github.com/nltk/nltk/pull/3759 (opens in a new tab)
- github.com/nltk/nltk/pull/3813 (opens in a new tab)
- github.com/nltk/nltk/commit/2a92b71827d754ae8920261e7ed0c4bb283ab2d7 (opens in a new tab)
- github.com/nltk/nltk/commit/a44a7af69bca87e92d9c4a701fcbbe4512e8d450 (opens in a new tab)
- github.com/nltk/nltk/commit/cbc98458b43de5f792f0382583c16df39e5c5117 (opens in a new tab)
- github.com/nltk/nltk (opens in a new tab)
- github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-3740.yaml (opens in a new tab)
- vulncheck.com/advisories/nltk-through-3.10.3-path-traversal-via-model-artifact-apis (opens in a new tab)