Staging Environment: Content and features may be unstable or change without notice.
Advisory details: github_osv / GHSA-3m7f-6hxv-6796
Advisory ID github_osv/GHSA-3m7f-6hxv-6796
Aliases
Summary Duplicate Advisory: Pl196xCorpusReader has quadratic ReDoS on malformed TEI blocks ## Duplicate Advisory This advisory has been withdrawn because it is a duplicate of GHSA-8mpw-7fpc-4gqj. This link is maintained to preserve external references. ## Original Description 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.
Status Published
Exploitability 0.5
Weighted Severity 5.7
Risk 2.9
Affected and Fixed Packages Package Details
Introduced and Fixed Package Commit Patches Package Commit Patches Details
Weaknesses (1)
CWE-400 Uncontrolled Resource Consumption
System Score Found at
cvssv3.1 3.7 https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/08/GHSA-3m7f-6hxv-6796/GHSA-3m7f-6hxv-6796.json
cvssv4 6.3 https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/08/GHSA-3m7f-6hxv-6796/GHSA-3m7f-6hxv-6796.json
generic_textual MODERATE
Reference id Reference type URL
https://github.com/nltk/nltk/security/advisories/GHSA-8mpw-7fpc-4gqj
https://www.vulncheck.com/advisories/nltk-before-3.10.3-regular-expression-denial-of-service-via-pl196xcorpusreader
CVE-2026-81725 https://nvd.nist.gov/vuln/detail/CVE-2026-81725
No exploits are available.

No EPSS data available for this advisory.

Patch URL
There are no known patches.
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L Found at https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/08/GHSA-3m7f-6hxv-6796/GHSA-3m7f-6hxv-6796.json
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: 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 Found at https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/08/GHSA-3m7f-6hxv-6796/GHSA-3m7f-6hxv-6796.json
Attack Vector (AV) Attack Complexity (AC) Attack Requirements (AT) Privileges Required (PR) User Interaction (UI) Vulnerable System Impact Confidentiality (VC) Vulnerable System Impact Integrity (VI) Vulnerable System Impact Availability (VA) Subsequent System Impact Confidentiality (SC) Subsequent System Impact Integrity (SI) Subsequent System Impact Availability (SA)

network

adjacent

local

physical

low

high

none

present

none

low

high

none

passive

active

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none

There are no SSVC decisions available.