EUVD-2026-67075
GHSA-3m7f-6hxv-6796
Severity by source
CVSS: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
Network vector but high complexity and no privileges required; impact is solely low availability via CPU exhaustion, no confidentiality or integrity loss.
Primary rating from Vendor (VulnCheck).
CVSS VectorVendor: VulnCheck
CVSS: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
Lifecycle Timeline
2DescriptionCVE.org
NLTK before 3.10.3 contains a regular expression denial of service vulnerability in Pl196xCorpusReader that allows attackers to cause quadratic CPU consumption by supplying malformed TEI blocks with many unmatched opening tags. Attackers can exploit lazy regex patterns in the read_block method through public APIs like words() and tagged_words() to force repeated rescans and achieve near-quadratic runtime growth.
AnalysisAI
Regular expression denial of service in NLTK's Pl196xCorpusReader allows unauthenticated remote attackers to exhaust CPU resources by supplying malformed TEI corpus data containing many unmatched opening tags. Applications exposing NLTK's words() or tagged_words() public APIs over a network boundary-such as NLP services processing user-supplied corpora-are at risk of near-quadratic runtime growth in the read_block method. …
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Vulnerability AssessmentAI
| Exploitation | Exploitation requires that the target application use NLTK's Pl196xCorpusReader (specifically via words() or tagged_words() methods) AND that it processes attacker-supplied or attacker-influenced TEI corpus data. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 4.0 score of 6.3 reflects network reachability (AV:N) offset by high attack complexity (AC:H) and an attack prerequisite condition (AT:P), with impact limited entirely to availability at low severity (VA:L). … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker targeting an NLP-as-a-service application built on NLTK submits a crafted TEI corpus file containing thousands of nested, unmatched opening tags via the service's corpus analysis endpoint. The application calls words() on the uploaded corpus, triggering the vulnerable read_block regex which rescans the malformed block repeatedly, consuming near-quadratic CPU time relative to the tag depth and stalling or crashing the service worker. … |
| Remediation | Upgrade NLTK to version 3.10.3 or later, which resolves the regex pattern in read_block. … Detailed patch versions, workarounds, and compensating controls in full report. |
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Same weakness CWE-400 – Uncontrolled Resource Consumption
View allSame technique Denial Of Service
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External POC / Exploit Code
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