Bug 2037526 (CVE-2021-3842)

Summary:	CVE-2021-3842 python-nltk: ReDoS in function get_pos_tagger and malt_regex_tagger
Product:	[Other] Security Response	Reporter:	Marian Rehak <mrehak>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED UPSTREAM	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	unspecified	CC:	jamatos
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2022-01-05 20:40:46 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2037527
Bug Blocks:

Description Marian Rehak 2022-01-05 20:09:25 UTC

nltk is vulnerable to ReDoS attack because of ^-?[0-9]+(.[0-9]+)?$ regex. If attacker succeeds to use malicious payload against RegexpTagger used in function get_pos_tagger and malt_regex_tagger, it will cause a nasty DoS.

External Reference:

https://huntr.dev/bounties/761a761e-2be2-430a-8d92-6f74ffe9866a
https://github.com/nltk/nltk/commit/2a50a3edc9d35f57ae42a921c621edc160877f4d

Comment 1 Marian Rehak 2022-01-05 20:09:41 UTC

Created python-nltk tracking bugs for this issue:

Affects: fedora-all [bug 2037527]

Comment 2 Product Security DevOps Team 2022-01-05 20:40:45 UTC

This CVE Bugzilla entry is for community support informational purposes only as it does not affect a package in a commercially supported Red Hat product. Refer to the dependent bugs for status of those individual community products.