CVE-2026-81726: nltk External Control of File Name or Path
Vulnerability summary
CVE-2026-81726 is a high (CVSS 8.3) External Control of File Name or Path vulnerability in nltk. EPSS estimates a 0.34% chance of exploitation in the next 30 days, higher than 25.9% of scored vulnerabilities. 1 public exploit is recorded.
Advisory lineage
Upstream 1 · Downstream 0Timeline
- 27-08-2026PublishedVulnerability first disclosed.
- 27-08-2026Last modifiedVulnerability information updated.
Description
NLTK through 3.10.3 contains a path traversal vulnerability in model-artifact APIs that bypass pathsec enforcement by using raw file operations on caller-controlled paths. Attackers can read or write files outside allowed sandbox roots through TransitionParser, AveragedPerceptron, PerceptronTagger, and maxent parameter APIs when pathsec is enabled.
CVSS metrics
10 scores · 7 sources · 2 versions- OSV · PypiEcosystem advisory · calculated8.3HighCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
- OSV · UbuntuEcosystem advisory · calculated8.3HighCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:L/VA:L/SC:N/SI:N/SA:N
- OSV · DebianEcosystem advisory · calculated8.3HighCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
- OSV · WolfiEcosystem advisory · calculated8.3HighCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:L/VA:L/SC:N/SI:N/SA:N
- OSV · ChainguardEcosystem advisory · calculated8.3HighCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:L/VA:L/SC:N/SI:N/SA:N
- NVDNIST8.3HighCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
- OSV · UbuntuEcosystem advisory · calculated7.0HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:L
- NVDNIST7.0HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:L
EPSS trend
Probability
0.34%
Chance of exploitation in the next 30 days
Percentile
26%
Versus all other CVEs
30-day change
+0.08 pp
From 0.26% on 20-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
1 foundNltk
Maturity: poc
Weaknesses
CWE · root causeAffected systems
Chainguard9 products
- apache-beam-python-3.11-sdkAll versions (No fix recorded)
- apache-beam-python-3.12-sdkAll versions (No fix recorded)
- apache-beam-python-3.13-sdkAll versions (No fix recorded)
- apache-beam-python-3.14-sdkAll versions (No fix recorded)
- label-studioAll versions (No fix recorded)
Debian1 product
- nltkAll versions (No fix recorded)
Nltk1 product
- nltk≤ 3.10.3 | < 3.10.3
PyPI1 product
- nltk≤ 3.10.3 | < 3.10.3
Ubuntu1 product
- nltkAll versions (No fix recorded)
Wolfi1 product
- open-webui< 0.11.4-r0
6 vendors · 14 products
References
15 links- github.com/nltk/nltk/security/advisories/GHSA-8mgp-746c-j5xpVendor AdvisoryWEBEVIDENCEREPORTAdvisoryExploit
- www.vulncheck.com/advisories/nltk-through-3.10.3-path-traversal-via-model-artifact-apisThird Party AdvisoryWEBAdvisoryREPORT
- github.com/nltk/nltkPACKAGE
