CVE-2026-81723: nltk Uncontrolled Resource Consumption
Vulnerability summary
CVE-2026-81723 is a medium (CVSS 6.3) Uncontrolled Resource Consumption vulnerability in nltk. EPSS estimates a 0.28% chance of exploitation in the next 30 days, higher than 19.4% of scored vulnerabilities.
Advisory lineage
Upstream 1 · Downstream 0 · Related 1Timeline
- 27-08-2026PublishedVulnerability first disclosed.
- 31-08-2026Last modifiedVulnerability information updated.
Description
NLTK versions before 3.10.3 contain a quadratic CPU exhaustion vulnerability in XMLCorpusView._read_xml_fragment() that rescans accumulated XML fragments on every 1 KiB block read. Attackers can provide malformed XML corpus files to cause severe CPU consumption and denial of service through affected readers like BNCCorpusReader.
CVSS metrics
11 scores · 7 sources · 2 versions- OSV · PypiEcosystem advisory · calculated6.3MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
- OSV · UbuntuEcosystem advisory · calculated6.3MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
- OSV · DebianEcosystem advisory · calculated6.3MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/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 · calculated6.3MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
- OSV · ChainguardEcosystem advisory · calculated6.3MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
- NVDNIST6.3MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/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 · PypiEcosystem advisory · calculated3.7LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
- OSV · UbuntuEcosystem advisory · calculated3.7LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
- NVDNIST3.7LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
EPSS trend
Probability
0.28%
Chance of exploitation in the next 30 days
Percentile
19%
Versus all other CVEs
30-day change
+0.06 pp
From 0.22% on 21-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Chainguard2 products
- nemo< 2.7.3-r27
- open-webui< 0.11.3-r1
Debian1 product
- nltkAll versions (No fix recorded) | < 3.10.3-1
Nltk1 product
- nltk< 3.10.3
PyPI1 product
- nltk< 3.10.3
Ubuntu1 product
- nltkAll versions (No fix recorded)
Wolfi1 product
- open-webui< 0.11.3-r1
6 vendors · 7 products
References
12 links- www.vulncheck.com/advisories/nltk-before-3.10.3-quadratic-cpu-exhaustion-via-xmlcorpusviewThird Party AdvisoryWEBREPORTAdvisory
- github.com/nltk/nltkPACKAGE
- pypi.org/project/nltkPACKAGE
